Most Helpful Girl
she is trying to make you jealous.
Most Helpful Guy
She's interested in you, she's either trying to make you jealous to make you make a move on her, or, she's attentive to when you look at her, she wants your attention, and she checks to see if she's getting it. Talk to her bro, maybe not to date, but, become friends with her, you never know what you might miss on :)