I cant stand my cousins?

So a few years ago my aunt decided to adopt a girl and I tried my best to love her and make her feel like a member of the family.

She's 12 now. (I'm 18 btw)Well,she's a very naughty girl,and in a non cute way,she's rude,obnoxious,disobedient,loud,annoying, has poor hygiene , basically a mess. She also likes to make up stories and "lie" about things.

On top of that , i caught her stealing my bracelets a couple times, she literally said they belong to her. but i didn't think much of it. Until the time she stole an expensive ring from my sister.

But this girl "claims" that she really loves me and she wants to hang out with me all the time and stuff,which makes me kinda feel bad about the way i feel about her.But i just can't get over the fact that she steals my things and lies to me. She's never going to change.

I don't know what to do, i don't want her to like me anymore, i've always wanted to distance myself from her but i have no idea how to do it. Oh and, whenever she meets with our other young cousin, (13 yo), they start judging the way i dress and say that i should "cover up", when my clothes are very modest and appropriate , just a little edgy. They literally got on my nerves, and their judgments actually hurt.

Do you guys have any ideas on how i should treat/ what should i say to make them respect me more and f off me ? and how to cope with all this ?