I HATE LIARS AND THIEVES!!!?

im 19 and i'm a sophomore in college. currently i'm living w/ my mom, sister, and brother because i can not afford paying rent, or living in a dorm....but i digress, my sister (15 in aug.) and i have to share a room, i wouldn't mind except for the fact that she is a compulsive liar and a thief. when i first moved in, it was ok. i stayed outta everyone's way b/c i'm used to living w/ my dad who always gives my space. when she wanted something, I came through: money, clothes, brownies (she's obsessed w/ them, but can't cook). lately (like in the past two months) she's been asking for a *** whooping. I noticed that little things would go missing from our room..for instance, i set my headphones (I LOVE MUSIC) on the floor next to my laptop and when I returned they were gone so i texted her where are they ( i just knew she had them). she got defensive and started saying she wasn't the one and why would she take it blah blah blah. next thing you know, i leave and come back and there right where i left them. i just shook my head and left it alone. then, other stuff went missing, my new victoria's secret bra (not her size), some of my clothing items, and just other items. I told her to put them where she found them before i came back from work and she was like "ain't nobody touched your sh**, i'm tired of you accusing me" so i went through her stuff and found EVERYTHING hidden in like pockets that she cut into her luggage, under her mattress, just random places. I took them back cause there mine, duh. i didn't confront her b/c she's old enough to know how ridiculous she is...oh she stole the bra again and when she was sleeping i saw it on her, IT'S NOT EVEN HER SIZE! my gosh. my mom told me that she's been like this with my other older sister that used to live with them and it's jealousy b/c she's always like jealous ALWAYS and I try my best to not do anything that makes her feel like she's not good enough (even though she's sooo cocky, i know it's a front) b/c she says stuff like she wants my body type instead of hers which is more athletic (and she has no booty, we're black so i guess it's required). Anyway, i'm just sick of her lying and i'm not a confrontational person at all, i just want out. unfortunately, the my job doesn't give me a enough hours or consistent shifts to do that. plus there isn't jobs around me b/c i need a close job since I have no car (tear). Any advice? b/c i'm about to lose it and i'm mad...and i'm not one to get mad easily at all. I absolutely hate thieves and liars b/c a) i'm family and b) i always give her what she wants plus more. I hate having to make sure i remember where & how I left my stuff when i'm away from the house or taking my purse everywhere, even when i'm in the house (oh, she's stolen money too). And the lying makes me even more angry b/c i'm FAR from stupid (don't judge me on my grammar & punctuation, lol...idc) and when someone lies, I feel like their basically saying, "hey i bet your dumba** will believe this". I also feel like a piece of sh** when someone lies b/c ppl ususally lie to people who they don't care about...like a bum, so if your lying to me that means you could care less about me. Wow, this is actually quite cathartic. thanks for your advice in advance (if any), or for just reading....i'm usually the one that's listening when my friends talk (psych major).