I don’t think you’re being too sensitive, man. When someone says, “That’s just who I am,” it can sound like your feelings don’t count, and that’s not fair. It’s possible for her to be friendly and still respect what makes you uncomfortable. You’re not asking her to change who she is, just to show a little awareness of how her actions land with the person she’s with. Maybe tell her exactly that, not as a fight, but as a truth: “I love that you’re outgoing, but I need to feel like you see me too when we’re around others.”