Ok family run down:
Husband with one previous daughter who is 12.
Me with one previous daughter who is eight.
Both girls stay with us full time.
We have a son who is almost 2 in common and anther one on the way.

My daughter is fourth generation only daughter in my family so she wants for nothing. She has a supportive extended family and is very smart and excels in school, she's athletic and not only made league soccer (American) but was invited to goalie training. She excels in most everything. Now his daughter is in stark contrast she hates school hates doing anything other than laying in her filthy room. I feel bad for her but that only gets her so much slack. My family had tried to treat her nice taking her everywhere with my daughter buying her exactly what my kid got etc. But it has seemed to stoke her jealously instead of helping it wane. She takes my kids clothes (what fits on her kinda) I mean she is TINY and will fight to get into my kids clothes swear they fit but when she sits down her large intestine hangs over the jeans I mean there's no fat on her but she doesn't seem to understand an 8 year olds clothes don't fit her. If my kid gets a present twice for her birthday she goads my kid into giving it to her. Instead of returning it and getting something else. She takes anything my kid has. I used to think it was because she didn't have the same type of stuff (me and her dad have been married almost two years) so I and my family evened her up with my kids belongings pretty quick. But they've been equal in stuff for about a year and she still takes my kids stuff she seems to not only want to be equal but she wants more. She hates on my kid for trying in school. My daughter loves her and used to really look up to her. Like the other day my kid was writing out an assignment and trying to use her best handwriting she was very proud and asked her sister if she thought it was good handwriting his kid leans over has and gander and says "it's ok for a 2nd grader". I laughed very loud. Because it's absurd my kids handwriting is head and shoulders above hers so I just whipped out a handwritten assignment of his kids done that week and it was absolute crap barely legible. I asked her flat out in front of my kid why she is so jealous that she can't just pay her a simple compliment. I told his kid if she practiced one day her handwriting could be as good as a 2nd graders. His daughter isn't smart as far a school is concerned she's been held back a grade and is still in remedial classes. I've worked with her but her problem isn't a lack of raw intelligence it's a lack of care. She only cares about socializing, talking, and boys. Her own peers think she's kind of pathetic when it comes to school and believe that her friends aren't academic scholars, they're average kids who probably slack off a little in school, and by their standards his kid is a slacker. But his kid is always manipulating my daughter into giving her material things or giving her special privledges without my kid contesting it. All if this coupled with her absolute disrespect towards me has made me disengage her. Disengaging her is very difficult though because her fathers job has him traveling ALOT sometimes being home only one weekend a month. He supports me in my decision to disengage with his kid and he is working in finding stations closer to home so he can be him or a place that we can relocate the family so he can be home more. I have her grandpa take her on the weekends but literally no one in her extended family have anything to do with her. Once a year her great grandma will take her to get her nails done but that's really the extent. I had to tell her grandpa how unfair it is for her to be with people who are no kin to her and as far as she's concerned an intrusion into her life. I just don't know what to do about her manipulating my kid I keep my kid away as much as I can she's only around her three days a week after school for the time being. But I cannot stand her. She lies every time she talks her aunt turned her out for the same issue. She hides things and insist she can't find it. She will hide things and ask her dad to help her find it. She cries if I don't let her get away with crap like sitting where she wants in the car. She will cry and swear the seat no one else has a problem with is poking her to the point of crying. She will not eat anything I cook which is cool I make her go to her room until everyone else is done which has made her stop complaining about dinners. But you have to disengage her to get her to stop acting like a total fool. She won't do her hair she won't brush her teeth if I do her laundry she literally throws it on her bed and sleeps in it. Her guns bleed her hair breaks off so it's always jaw length because she won't remotely take care of it. She's embarrassing to take out. I've bought her hair products and tools and have showed her how tondo her hair, I think it's her way of giving me the middle finger by just not taking care of herself. She ignores my son unless her dad is around. She is very hateful. She's always fighting with her friends. Her teachers say she is sweet and she definitely can be but I really think they say that because they don't have anything else positive to say in the meetings we have to have all the time because of her remedial classes. I mean everyone always told me I have it easy with my kid but I don't think I understood what kind of chaos and tension a kid could cause by simply living in a house. When she is not here things are nice and enjoyable but the minute she gets home I have neighborhood kids yelling on my doorstep because they're fighting with sd or the girls are fighting because as is trying every trick in the book to get her way and my daughter is starting to catch on. I'm just at a loss anymore. I don't like having someone in my house I can't talk to beyond co-habitant otherwise there is flares ups and endless drama and manipulating. She goes to therapy they've got nothing except she to tell us the obvious she has self worth issues and is likely to take her offbeat obsession with gaining material things will most likely eventually evolve into drug problems or promiscuity. I don't want my kids around her but barring a divorce there is no one else who will take her. I've tried to help but she seems to enjoy doing the polar opposite of whatever advice I give so I don't give her any. Then she resents that I don't talk to her. I can't win but in this weird limbo of a time I cannot win and just hope something resolves itself. Because if I end up having to resolve it the only option I can think of is divorce.