She obviously likes you enough plutonic level wise and knows that you like her and it sounds like your interest in her is probably giving her an ego boost.

But if she has a boyfriend then there's not much else further this can go unless one of you makes an obvious attempt to "cross the line".

If she made negative comments about her relationship with her boyfriend then that would be one major kind of indication that she is suggesting that something could happen with you. But if not I think it's just that she sees you as a friend who gives her the occasional ego boost because of your obvious interest.