What's her problem? what is she trying to do?

She's trying to make you jealous. Don't let her get into your head. The next time you see her, ask her why she did that. Make her give you an answer. If she doesn't give you a straight answer, then she is either afraid of you or wants to avoid the question. If she gives you an answer (which I highly doubt), then go with the flow. Be yourself and maybe you can figure out why she did that. Hopefully your best friend with back you up. Good luck hun =)