Why is my little sister so mean?

[WMA]

Im 15 and my little sister is 11 we also have an older brother who's 18, my little sister is the one boulder rolling down hill forcing me to run into the suicide pit and just enter endless bliss. main problems include teasing, stealing and just pure hatred, she doesn't care about my stuff and doesn't share or does anything that will help me. when she requests to play or use the computer i simply just get off and give it to her without protest. i share,care and have to look out for her because my older brother is in college. she doesn't give a rat-shit about my feelings and my feelings have hardened quite a bit but it's the simple hindrances that cause the most damage. I've dealt with this and plainly ignored for about 2 years but its a nonstop tidal wave that just harrows at the beaches infinitely. I've tried talking,waiting, and even bribing but she just says "wtf you want you stalker?". when i walk her home from school she keeps a fake "happy" appearance so she doesn't look bad in front of her friends, all the schools I go to, I make a bond with my teacher and school is easy but she makes it more stressful because she refuses to get off the computer. I've used common sense and argued with her but she keeps changing the subject and I've tried counter teasing but she just fake cries and bitches. she's a suck up and a damn thief, one tactic I have yet to try is to break the will of her soul and spirit. I have yet to try this because its a risky gamble and It's against my morals to beat the shit out of her, but a person can drive another to desperate things. I grew up an obedient child only arguing when i think what i'm doing is total BS and I never complain and whine that i can't do this, I do my best and never give up but you can't have the strength of Atlas. I do my best to appease people but i've given up hope and is tiring of this conflict. I wouldn't mind suicide except I want to see what lays in my life and I would like to see what I impact in the world. I know you can wait it out for her to mature and finally realize or become self aware or you move out but I lack patience. I'm giving up the fight because i cant fight back at all, it's like WW2 USA vs Japan, me being Japan I can only fight for so long. i don't like to spend money and i just got a phone this year. my sister uses my money and is getting a phone. she also has FB,tumblr, and twitter and an email too. I am polytheistic and is open to all statements and comments and suggestions, I would like somebody to kill me but It's not gonna happen. My theory on why this is happening is because it dates back to when she was about 7 or 8, i couldn't play with her because I was so busy with homework and i failed to keep my self promise to be her brother and model. with that failure comes a price of her hatred and Idgaf independence/personality. I would love to ask Dr. Phil this question but i wouldn't like to waste his time or i would get the same answer. also my little sister would act "like the darnest thing" and i would look like some insane crazy faggot who deserves to get shot.

To all everyone who contributed, thank you and to those who say i'm a total moron and complete fag, well... I don't blame you and i welcome the bullet coming to my head, giving me forever peace even though it would be in hell and I would regret it., I would love to change time but i know I can shape the future I just want guidance and support from people who would like to lend a hand. I would like you to control my hand and tell me what to do.
MewWinx96, you are so awesome and so true