I am desperately needing some help or advice. I have been with my girlfriend for going on three years now. We have bought a house together. She has a 15 year old and a 13 year old daughter. Me and the 15 year old get along okay. The 13 year old is an entirely different story. She is extremely rude, hateful, and entitled. For example, I bought her and her sister cell phones for Christmas. 15 year old was thrilled. I promise to pay the bill every month for them. The 13 year old threw a fit. She didn't want an Android, she wanted an iPhone, and said that she refused to use the phone that I bought for her. She then went to one of her rich little friends houses and had her mom buy her a new iPhone. She constantly does things like this, says that we can't afford to take care of her and buy her the things that she wants, and makes her friends parents feel bad for her and buy her what she wants. We just moved into a new home, it's a single wide mobile home, but it's nice. She says that she is going to refuse to ride the school bus, because she doesn't want her friends to know that she lives in a trashy trailer house. Makes her mom late for work every morning. She says that she's going to ride the bus, but every morning it's a different excuse as to why she missed it. All of her friends have nice four and five-bedroom brick homes out in the country. She has her own bedroom here, we have internet, and she has her own flat screen TV in her room. But she tells people that we don't take care of her. She has not been home for two weeks. Her mother confronted her about it the other day, and she says that she refuses to come home because she hates me.  she says that I am not her father and she doesn't need to do what I tell her to do. I yelled at her one night and told her that as long as she lives under this roof and I'm paying the bills, that she does not have to say that I'm her father, but that she needs to respect me. She has admitted that she's trying to tear me and my girlfriend apart, and that breaks my heart. I don't want her to ruin the best thing that's ever happened to me. My girlfriend has stayed by my side through illness and some very difficult times. What can I do to try and save this relationship? My girlfriend is very upset that her daughter refuses to come home, but also refuses to discipline her. She will agree upon punishment with me, and then undermine what I say and turn around and give the daughter what she wants. For example, one time we agreed to take her cell phone away for a week. The next day, the girl threw a fit and her mother gave the phone back to her. There is absolutely no structure and discipline when it comes to this girl and I have no clue what to do anymore. Please help in any way that you can