Why is she acting like this?

[Sarah]

My sister is being ridiculously. She is so obsessed with a boy. She cares what she thinks of her so much. Just bc he likes girls a certain way she changes to be his type. If he likes red heads then she dyes her hair red if he likes brown eye girls she wear contacts. She thinks badly of herself just bc the boy doesn't like her. She thinks its bc shes not super skinny or tall. she has many pics of him on her laptop and on her phone that she gets from facebook. She is at his house 24/7. My mom and his are friends and his mom likes my sis and I. So she invites us over all the time. When we go over, my sister goes in his room when he isn't there and sleeps on his bed. She goes only to see him. She stocks his facebook profile and gets jealous when he comments on a girls pic. Today she found out he had a ex girlfriend and she got upset bc she thinks that bc he had a ex that means he is obsessed with girls and he would be looking for another girlfriend and she said she is sad bc she won't be one of them bc she isn't like the girls he likes. She says the girls he likes are know it alls and are the type to show off and she doesn't even know them, she just judges them from their pictures that she looks at on facebook. she is just saying that bc their skinny. She is also always moody and yells at everyone. When someone doesn't do anything her way, she gets pissed. Its her way or the high way. if she doesn't get what she wants she freaks out. She thinks everyone around her lives just to please her. idk what to do anymore. my sister and I don't live together and I still want to contact her and have a relationship with my sister but she is so hard to put up with. she lives with my mom and I live with my dad. i don't wanna get her mad by telling her how i feel bc she will be so mad and will stop talking to me. Every time she gets mad at me she stops talking to me and starts acting like she is all that and trying to get me mad by doing things I hate or exposing my secrets. One time she stopped talking to me for months and it really hurt. My mom takes her side, so when my sis gets mad at me, she does to. My sis knows this really hurts me and I try not to upset her bc i don't want my mom to hate me and she knows this so she yells at me and flips out on me bc she knows I wont do anything anymore. I tell my mom, she says ignore her then she flips out on me when my sister complains to her about me. My sister is 18. She asked me for advice ad I tried giving er some but she flipped out on e bc she said I was saying all the wrong stuff. I was telling her to relax a little. She said I am suppost to be making her feel better. If she knew what she wanted me to say why ask. She doesn't even talk to the boy. She just stares at him.
srry for the bad spelling and grammar

[Jazmin]

WoW..