My sister has a mental problem?

My sister is 22 years old and 5 feet tall 98 pounds. She has problems because she slobbers on herself when she is laughing or staring at something. She goes out with her friends and she drinks and she has ped out in dog kennels, she hides her facebook posts from me i have 3 brothers and another sister that lives with me she talks to non of them. she stays in her room upstairs all day on the computer non stop. She only goes downstairs when she wants to go out with her friends. She has new friends every other week and we have only met 3 of her friends since she has been going out since she was 18. shes had about 8 or 9 boyfriends and we"ve met none but they still come over to the house but she goes right to her room or stays on the trampoline in the backyard with a blaket all night. She has never introduced us to any of her friends or boyfriends. She goes to tempe at college parties without telling us she lies about what shes doing where shes going and who shes going with. She tells her friends to stay in their car and wait out side for her rather than knock on the door because she doesnt want them to meet us. Her boyfriends she has been dating since feb 14, has been to our house like every other night and we have yet to meet him. I try to look out the window when he comes to get her but she yells at me to get out of the window and i think she ashamed to be black because she is half black and half chinese but she is light skinned like she is just white or something. My ohter sister is also half black and chinese but they are complete opposites. Me and my brothwers are all black and spanish but we are darker skinnned. We went to disneyland because my brother wish that for his MAKE A WISH and she only put on facebook a picture of her and my light skinned sister like she is trying to hide the fact that she is black. Her friends are all WHITE no blacks, mexican, or asians. nothing but white. The first night she started dating this boy on feb 14, his name is chris, he took her out to dinner and when she came back home she forgot and left the damn CAR AND HOUSE KEYS in the lock on the front door outside. So the house keys were outside all night, in the door handle where anyone can get to it and come inside and do something to us all. We live in the most dangerous city in the state. She forgets a lot of stuff and she lways has to be told what to do. SHe doesnt clean her room only when she wants company and when she has a bofriend she acts like a hoe and does things with them and they just dump her the next day, I dont get why she doesnt gewt it. im only 15 years old and i know more aboutg things than she does. She wears fake hair, wears 3 pounds of makeup, and dresses like a . I dont know what to do about her because she used to be so smart and since she made a myspace she has not been the same. also she has not been the same since she star5ted dating chris. she hides big bottles of vodka in her room and she steals stuff all the time. from stores and she is going to get caugte one day. she steals VERY expnsive things and she cant go out of a store unless she has stolen something. She has gone out with almost everyboy at her joba dnshe is not supposed to do that or she can get fired. this boy, chris just came from texas and has no friends and doesnt know anyone. his cousin works with my sister and i think she is setting my sister up to get fired or for someting idk what yet though. She falls for boys to easily. You cant even hold a conversation with her or shell start texting in your face very rudely. SHe talks like she is a babny when she talks to other people like her friends. WHen she goes out with her friends she leaves the house at around 10 or 11 oclock. AT NIGHT and doesnt return until like 4 5 or 6 in the morning. I dont understand what is wrong with her. SHe is very naive and doesnt listen to the warnigns my mother tell her. She trust everyone she knows and everyone knows you cant do that. DO you think it was right for her to put only the picture of our light skinned sister on facebook instead of everyone? and yes we took a family photo and she didnt even put that one up. She goes to parties that are wayy far away from home and she changes her clothes once she gets out to look more like a slut. she takes half naked pictures of herself and posts them on facebook. She deletes me and my brohters from her facebook and myspace so that we cant read what she does or writes. She has never brought us food from her job like normal families and she hides money from my mom. When she knows that she is supposed to help out my mom with the house and bills and stuff. She allows her friends to control her like she goes out with her friends all the time and she never tells them that she is too busy to go out with them because she is out with us, instead she just lies to them about what she is doing. Can you tell me what is wrong with her and what i need to do to make her normal again? Im sorry this is so long.