What do you think I should do (or not do) in this case?

It sounds like she's got the jealousy issues. She may be pretty but it sounds like she still views you as a threat. Most likely because she sees some attractiveness in you and she is jealous of the prior history (meaning friendship, experiences etc ) that you and your guy friend have. Obviously you can't force someone to like you and if you haven't done anything wrong, then trying to be her friend is a waste of your time.