recently my ex boyfriend's 15-year-old daughter let our 10-month-old baby fall off the bed and I truly believe it was intentional.

I raised step dd for 7 years from age 5-12. Me and my boyfriends first child was only a few months old when she came to live with us. Now, step dd is 15, and our three kids together are ages 10, 6 and 10 months. Me and the father are not really together anymore, but we are good friends and we co-parent from Different households. Step dd recently returned from living with bio mom for 3 years and now she's back living with her dad. Long story short she's a very disrespectful kid and she's very jealous-hearted and she has always done malicious things that I have seen with my own eyes. She has a ton of enablers around her including her grandmother, her aunt, her godmother and to a certain extent, her dad. I'm the only one who knows the extent of how deep her lies go and the length she's willing to go to cover up her bad behavior. When I was raising her I did everything I could to teach her good morals, ethics and to be respectful. It was always a power struggle because her enablers didn't want me chastising her and whenever she did anything wrong, they would diminish/downplay what she did and then buy her expensive toys/clothes. She was always rewarded for bad behavior. She hates that I'm with her dad and she's mad that her sisters have spent their entire life with dad and she didn't come around until age 5. This is her mom's fault. Her mother gave her someone else's last name and didn't tell step dd and boyfriend about each other......he found out by receiving child support papers in the mail. Long story short, she has always took her anger out on her sisters and she is VERY disrespectful towards me and her dad. She likes talking about her dad to others and making fun of how her mom calls him "retarded". She knows this type of behavior wouldn't fly if I lived there. This is why she has wanted me out of the picture for so long. And the grandma too. She wants step dd to run the show because they both dislike me.  I tried taking her to lunch and having and heart to heart talk with her when she came back in March 2021, but she was being passive aggressive, throwing slights and still lying. She wouldn't admit to calling me a "hoe" via text, calling and playing/pranking on my phone and stealing my sweater when she came to visit a year ago. So, after the lunch, I have kept my distance. Dad is having an extremely hard time with her. He vents to me constantly about how she talks to him like he's a child, and how her attitude stinks. And it does. But, he also is a pushover and passive when it comes to discipline because his mom defends her and he doesn't want to go against his mom. It's so bad, he feels extreme pressure to cater to step dd....he was giving her $60/wk to wash dishes. This is more than he is giving me for child support for our 3 kids. He's also a huge procrastinator and ignores half of her bad behavior. He was like this when we lived together also. He's also like that with his mom and the god mom. And I'm sure you guessed, the grandma makes blatant differences in the kids. Caters to step daughter while she's mean to my kids and even calls them "weird" because they're not materialistic like step daughter. 

So, a week ago, my 3 girls were visiting at their dad's (they go 2 days a week). And she was being very snotty towards them. Dad asked her to hold baby and not let her fall off the bed, and two minutes later, baby fell off bed. My 10 year old called me whispering and told me. Dad believes it was accidental. I Know better. She's always been that type of kid. She would hurt my 10 year old constantly when she was a baby and dad and I would argue about it because he claimed he didn't see it as intentional. Right now, he complains about her being underhanded and disrespectful but he straddles the fence because the minute I get upset about something he disagrees with me. I have seen this kid hide things and lie for days saying that she didn't know where it was. I have seen her knock food off the table and claim it was on an accident. One time when my 10-year-old was a baby I came home and she had dust and hair off the floor in her bottle and dad didn't even notice. She was the only person who would have done something like that...there was no one else living with us. She would also manipulate her dad's family by making them think we were not buying her anything for Christmas Even though she was getting a ton of gifts from us. I remember one time she lied on the daycare provider and said that the daycare provider was hitting her, so me and her dad comfronted the daycare provider about it and it turns out she was lying on the provider. She said she was mad the daycare provider would not give her any candy. The daycare provider no longer wanted to provide care for us. I remember one time when my 10 year old was a baby, her hand got slammed in the car door and step Dd just stood there and watched her screaming for a long time and would not help her. I remember one time she saw me and her dad scrambling looking for his car keys for a very long time and she just stood there and watched us and it turns out she knew where the keys were at the entire time. We would get constant complaints from her teachers and daycare providers and people often said it seems that she had no respect for authority. ...I could write a book. ....So it's not just me saying these things. These things pushed me to separate from him and I moved out into my own apartment. I was convinced that this child had some serious problems and would hurt my baby if given the perfect opportunity. We all reunited a year later and the bad behavior continued. She just became better at hiding her sneakiness. She would manipulate her dad and put fake tears on her face with water from the sink and he would fall for it and when I would tell him that I saw her put water on her face he would basically ignore me and act like I was lying. So now it's to the point where even though he and I are separated and we try to keep a good relationship she is still causing problems because he and I are still having disagreements about how she is treating her sisters and more recently when she let the baby fall off the bed I was really done after that.. he knows her bad behaviors because he admits to a lot of them but it seemed like whenever it's something that I bring up all of a sudden he's in denial and he doesn't want to say anything to her about it. I had enough of her hurting my 10-year-old when she was a baby and now I'm dealing with it with our new baby. (She would be nice to my middle child in order to make my oldest feel jealous, so I don't have any stories of her being mean to my now 6 year old). Her jealousy and hatred and anger are misdirected at the wrong individuals and I'm tired of my children getting hurt. Should I stop taking my kids over there? My 10-year-old and 6-year-old are older now and they can protect themselves and tell if they need to. She's mean to them, but they ignore her and go in their room. But the baby cannot defend herself. My 10-year-old says that she thinks that her step sister puts things in her food and I believe her because when she would get mad when she was younger, she tried to spray my food with disinfectant. She also wet our toothbrushes (me amd my daughterys). She refused to say what she wet it with. i believe it was toilet water . I threw them away and bought new ones. Every time my girls return home from visiting their dad, some of their items is missing....shoes, glasses, phone etc... She steals for sure. She just got caught stealing at the mall with my sisters daughter (a relationship I disapprove of) right after she moved back with her dad. My niece has never stolen before, but step dd has several times. Any advice would be greatly appreciated. I'm really fed up with her abusive ways towards my kids, and dad is not putting his foot down. She calls his mom and tells on him like he's a kid and recently told him she doesn't want to wash the dishes anymore and she called her godmom and asked her to mail her paper plates and plastic silverware and her God mom actually did it and Dad and God Mom got into it over the phone and she hung up the phone in his face. 

I know in my heart that a lot of the negativity he is receiving from the God Mom and his mom and his daughter is actually negativity that they want to direct at me but they can't because I am out of the picture in my own apartment and taking care of my kids. All of the women that I have named off are very jealous-hearted and they are mad that I'm an independent woman who takes care of my kids very well and I don't ask them for anything. The god mom is jealous because as soon as step dd came to live with us, we got close and step Dd started calling me mom. This made her mad because she had been raising her with girlfy, who was step dds aunt. She taught her a lot of inappropriate things, including sexual things that she witnessed at the drag parties God mom would throw.  All of these women have been trying to break me and Dad up for a long time and they have all had an impact on our relationship. Her bio mom is abusive and neglectful and she's also jealous because she still wants a relationship with dad. I told my ex, if he ends up with another woman she's going to have to be a doormat because the amount of women trying to control his life and disrespects him and his relationship is insane. I dealt with it for years and had problems with all of these people and I just got fed up with it. He turns a blind eye and doesn't want to deal with it so when I bring up the problems he ends up blowing up at me. They know this, so they keep doing it. Especially step dd and his mom. His sister enjoys the drama, but I think her husband has more sense than her, so her interference has calmed down since she remarried with him and finally had kids of her own. Also, the grandma's husband is very fair and tells her she wrong in a lot of situations. 

I'm honest to a fault. I'm a good hearted person. I've put up with disrespect from his family and even from him. Hence the reason I moved out (again) and decided to raise my kids separately. But if I stop taking baby over there, dad will be mad. But I don't want my baby being mistreated. He allows her to get away with a lot and he's either blind to it or he ignores it. What do I do?