Why is my cousin such a spoiled brat?

My sister gets everything she wants and i'll just list a few things she has! First of all she is 9 and she has 5 pairs of miss me jeans, 3 ugg boots, juicy track suit, prada purse, coach purse, 2 coach purses, 1 juicy purse, an iphone 5s, a 3ds, vera bradley tote, macbook pro, louis vuitton bag, 2 pairs of beats hadphones, real diamond earrings, pink motor scooter, 7 american girl dolls, her own walk in closet, a pet rabbit, kitten and rat(like she takes care of them but they're stuff annoying), a 60 inch tv in her room, 4 tiffany necklaces, a pandora charm braclet, chanel and gucci glasses, a king sized bed, an electric piano, per own private bathroom filled with victoria secret and bath and body works merchandise, 200 dollars worth of nail polish(but only like in girly colors), 4 (victoria secret)pink yoga pants, a pink hoodie, 5 regular bras from victoria secret and a push up bra from there, a bag from italy my grandmother gave her, 2(victoria secret) pairs of pink sweats, like 5, 000 dollars worth of cosplay, a hot tub in her bathroom, a hair straighner, curler and crimper, sleep overs every week, she gets to dye her hair light pink, she gets starbucks everyday, she gets 100 dollars of pocket money a week, goes to the spa every friday after school with my aunt(she gets manicures, pedicures, facials, and hair treatments), her makeup is only from nars, mac, and sephora, she goes to an expensive school that teaches her dancing(ballet, jazz), singing, acting, art, and fashion design, she goes to concerts all the time, she has her own credit card, has over like a thousand stuffed animals and she's been to ilaty, germany, tokyo, england and basically all over the world. You may think that's bad but that isn't even the worst of it! I'm emo and she is a mixture of preppy and kawaii omg you don't know how bad that is. She dresses in like lolita, pastels, florals, lace, hello kitty, princesses and basically anything cute(i mean like 9 year olds are suppost to wear like mini skirts and crop tops!). She'll do her makeup in the bathroom with me and she makes her's all natural and stuff i don't see why people call her pretty anyway i was putting on my eyeliner and red lipstick trying to look hot when she tells me its not good for my skin i mean she's such a brat i know what's good for my skin thank you! She always liked lame stuff like anime and cosplay you know nerdy stuff so like when i found out my crush likes it i went into her room to like take a few things from her and she like yells at me for trying to steal, i'm the older sister and when i told her it was an emegereny she didn't believe me! She'll be playing her piano in her room and i can hear it so she tells me to study out in the rose garden when i can't hear her what a brat! My mother made me take her clothes shopping once and she only wanted "cute" dress that where at the knee i mean how lame is she i tried to get her into something shorter but she throws a fit and says "i don't want to look like a slut i want to be modest." its so freakin annoying! She gets like straight a's and b's and ill get like c's like any normal child and everybody praises her for it i mean can you believe that! She's like freakin rich but hangs out with losers i mean she wants being nice to a blind kid and a kid with cancer doesn't she know cancer is like a skin contact disease, we'll be like walking anywhere and people praise her for how "beautiful" she is, guys hit on her all the time and tell her how pretty she is and she doesn't flirt at all she's wasting her talents! She like helps out in soup kitchens, gives away clothes, and raises money for the city i mean like barf stop trying to be perfect, The absolute worst part is how modest she is, if i insult her she smiles at me and says thank you in her annoying squeaky voice it drives me nuts! I mean what should i do about her? I tried everything to change her but nothing worked! She could have been goth, scene, punk or even a metal head but no she had to be a brat instead! I mean should i kill her i hate her so much my blood just boils, i tried to but my mom like grounded me and took away all my weed, please help i just want my cousin to be normal like me.

Blame the parents.

What's wrong with cosplay and anime? Honestly, YOU'RE being a brat. Who cares? Just relax. Cosplay is actually really fun.

Youre the brat here.