How to get my cousin to leave me alone?

I hate it so much, one she's older than me (weird right?) and two she's so annoying. I'm 14 and i live with my mom and grandma (small *** house).It's ridiculous! Her 5 year old sister(also my cousin) runs yelling around the house and i can't take it anymore. And she's 18 without a phone and always just takes my phone and goes an fb or whatever. I'm too nice but i'm gunna go off soon. To top that off she dropped my phone which cracked because its an iphone. And to top off dropping my phone, she's going to be living here. My life sucks right now. Her father(my uncle) just brings my little cousins over and they eat all the food and we barely have any money to buy more. They are here nonstop and its driving me and my mom and grandma crazy. She's on the bed with me as i type this using my phone. She won't get out even though i tell her i have homework to do. Its so frustrating because she knows she's annoying me and she even asked and i said yes. Please help me i'm dying and need my own space.

Added (1). Haha my iphone is really old its a 3gs which i got for my birthday a couple years ago. Things have gotten really bad since then so yeah.

With family its difficult.sometimes you just have to suck it up and just get over it. Yea she might be annoying but she is family. If they are eating all your food tell her to get a job and pitch in to the grocery list. Or better yet tell your mom and she could tell her that if she's going to be around she should contribute. Specially that she's 18 years old. But if you have an iphone money can't be that bad. Just saying.

Be straight up with her. Tell her you don't like her, she annoys you, and you don't want to talk to her. Out your foot down. Or when she's there just leave the house or ignore her.