Here is one for you. I am a step mom with no children of my own. I all of the sudden had a 2 1/2 year old and 7 year old. For some reason, their mom and I became close, in fact we have formed sort of a family unit. Her new child, calls us his second home. He keeps his turtle in our basment so he can visit it every other week when his stepdad comes to get the girls. He also taks his dad to visit.
I really think you should talk to your dad, or someone at school. Maybe she does not realize what she is doing. I know sometimes I got into a habit of going to our basement to work, due to my job. I also would close my door just to watch a show. Then I realized that wow, there are things they like that I also like. I hate to play games, but I love to shop!! I hate to sit and watch them play games, or look at things on the pc, but in a heart beat I will take you to lunch, or I will sit down and watch a movie with you. I will sit in our basement with the dogs with you all evening, talk watch tv, what ever you want.
I learned that they did not pick me, their dad picked me, they are stuck with me. So you have to find a way to her heart, maybe she thinks the same as you. Maybe she has fallen into a pattern and not realized. It has been 7 years for me, yes there have been hard times. But most of them have been great times! I would not change anything. Sometimes us adults get stupid and just think well you just want to do your own thing, but you really just sometimes to talk to us. Try this, sit her down, talk to her, let her know that you want to be a happy family not looking forward to your move out. Let her know that you want to get to know her and you want her to get to know you. It might take time, but I had the support of their mother in the first few months of moving in with their dad. She was there for me to talk to, she was there for me to say, hey I don't like to do this, but I like this....so we came to an agreement, I will take you shopping, be here if you need to talk. Cause she likes that game thing!!
maybe give your dad a heads up, let him know, he might not even realize what is going on. Work on this full circle, and try to involve your other set of parents if that is possible. I think sometimes its harder for an adult to act like one than what we expect from you. I wish you luck.... Don't them put you in the middle if you try to involve both sides. I can tell you, getting to know my husbands ex has been the best thing I ever had done to understand these girls. Its hard sometimes to co-parent, but sometimes you have to remind them that you were made from love, and that love might be gone, but the love they had for you will always be there. So they must stand up and put you first!
My stepgirls are happy, they know I am here for them, they know I will back them, and that I love them!