unbelievable!

i don't understand. when my sister lies to the parents about things going on in her life i stick by her, even if it means that i too end up lying. but then i ask for the same courtesy and she gets mad. I have decided to move back to my moms. its a difficult thing for me to do because as i said before no one thinks i should, but my sister made the decision even worse for me. i got an acceptance to a school by my dads which is great but i already made a payment to the school at my moms. I don't really feel like my mom even wants me here but this school by her house is amazing and i already have a few books and credits to the course I am taking so it would be easier for me.My sister opened my mail without my permission read my mail and told my mom about the acceptance. And now my mom has been acting strange like shes waiting for me to tell her okay never mind i am not moving. But I love this school!! so now my sister is all mad at me and telling me i am a horrible person and breaking my dads heart and all this crap. like how dare she talk about these things. she shouldn't have even opened my mail and yes i am moving but to go to school and a great school she should be happy for me. no one is happy for me then she ends with "great living with you" like are you kidding me!!! i understand she is mad but im trying to get an education!!! why would she do this and make me feel so horrible. I am doing this and no i dont care how people feel because at this point its back to thinking about me