How do I keep my female relatives out of my life?

I am a 20 year old female college student. I live in an apartment with my long time boyfriend. Being in college puts me at an advantage because most of my family have never gone to college and are constantly struggling with money. On and off since I was a teenager, 2 of my female relatives(my aunt and older cousin) have acted very catty towards me in particular. My cousin is in her 30s with 4 children, never went to college, is a former crack addict, and has money issues so bad BOTH of her parents still pay her bills. Generally she is nice to me, but can turn quickly. She told my boyfriends mother to "watch out" for me because I was "manipulative". My aunt stares at me a lot, sometimes with a disgusted look on her face. She has made snide remarks to me and I've eavesdropped on her telling my mother that I thought I was "hot sh*t'. For awhile she would seem to copy my style too. This sounds ridiculous and immature to say, but when I would see her I would be wearing a certain pair of earrings and then I'd see her a couple weeks later and she had magically bought that same pair of earrings and was wearing them. It has happened several times. I would often stress myself out trying to understand why my aunt is so snotty towards me, then my boyfriend said, "I don't think she hates you, I think she admires you and wishes she had a daughter like you." This does make sense considering I have shown more potential than her daughter ever did. Regardless of their reasoning, they make me feel very threatened and I don't really want them to be a part of my life. The problem is that our family is very close, we live in the same city, and my family is close with my boyfriend and his family as well. Also, I have expressed my dislike for these women to my mother, who gets mad that I don't like her sister and niece. So since my mother won't help me out, and she tries to guilt trip me to go to family gatherings where I'm forced to see them, I don't know what to do. The obvious thing to do would be to stop going to family events, but that also is rude to my other family. How can I stay away from my aunt and cousin?