Situation 1:
When I got an iPhone, she wanted to see it, so I let her. She sent terrible texts to all my friends, laughing. Then, a few months later, she got an Xperia U. All my friends carry iPhones, so I've never got to check one of those out. When I asked to see it, she rudely said "no, it's mine".
Situation 2:
I have no problem with her borrowing my clothes, but she never gives them back. The clothes she does give back, however, are torn, dirty and/or stretched-out.
Situation 3:
Whenever she's upset, I comfort her. Whenever I'm upset, she laughs and walks away.
Situation 4:
She's always telling me I'm ugly, fake, look anorexic, stupid, etc. I don't usually say anything back, but once I did, she started crying and told her mother. Then, I was grounded for 2 weeks.
Situation 5:
She's always stealing money from me. She keeps whining on how she's poor and her parents won't buy her anything. I feel bad and get her stuff, occasionally, but she keeps asking for more and starts stealing stuff from my bedroom.
Situation 6:
She acts like she owns me and always bosses me around.
Situation 7:
She acts like she's better than me, flipping me off and being a diva.
Sorry if this is long. What should I do?
Added (1). I'm 15 and she's 12.