We pretty much all can exhibit borderline personality traits at various times. Have you asked the woman about her behavior? Have you said something like "I wish you would stay around longer?" or been in a one-to-one relationship with her so you can observe her behavior better? Often a person can seem one way or another because of our own perception of them. It's kind of like don't think of:



but you have to because I mentioned it. Like deciding you are going to buy a red car and suddenly you see a whole lot more red cars than you used to :-)

Do you have an interest in this woman? I would get to know her better and talk with her more, etc.