Why do jealous women like to stare at you if they don’t like you?

I have a cousin that loves to stare at me every time I come over. But, I notice she always makes a disgusted face or irritated face at me. She’ll study my outfit, face, and hair. It’s so weird. She’s said before that if I ever went out with her men would approach me first. But, it’s weird that she’s like studying me. If I make a comment about men she just makes a face. One day I was smiling talking to my other cousin and across the room she looked so irritated at me just staring at me. By the way she’s a pretty girl too so, I don’t get it.