This is my first time posting on here. Just really need some advice or someone to tell me if I am being the bad SM... 

I have two skids...a 15 year old boy and 10 year old girl. They are both really sweet children honestly. I try my best to see all the positive things about them. My SD is my biggest problem ever though. She absolutely drives me crazy. She is her daddy's little "princess." She does nothing wrong ever in his eyes. Since their dad and I have been together she has always been right in the middle. We never go on dates due to having her with us ALL the time (well every weekend). If by chance we do get to go on one, she will call and beg him to come and get her...and our plans are ruined. She will completely destroy our house and he will not make her clean one single bit of her own mess. I clean up after her more than I clean after all of us combined (if that makes any sense). I have kept her while he has worked more times than I can count and she is very disrespectful (that goes in many different directions). She got on the bus one morning with her hair in a tangled up mess simply because I told her to brush it. Her mom calls the next day angry because I let her get on the bus looking the way she did. I am the bad person obviously. It's getting worse and worse. I absolutely dread coming home and seeing her on Fridays and I hate that. I want to be able to enjoy the time that they are there.