It is possible that she felt overwhelmed 3 yrs ago and just wasn't mature enough to handle the situation. Sometimes it's easier to walk away and ignore the feelings (seemingly acting bitchy when in fact it was avoidance due to personal issues/immaturity). Now, she probably regrets how she behaved and doesn't want to be that girl anymore. I'm sure it wasn't easy for her to reach out to you. It is possible that she's had a recent break up that is making her more emotional. Maybe/maybe not. You have to evaluate the situation and how it works for you. If you could be friends with her (or maybe more) or even if you're just curious then meet with her. If you do meet, even for a casual coffee, then that would be the time to ask her about why she acted the way she did and tell her how hurtful/bitchy her actions were toward you. You sound like you're in a pretty good place so if she started acting bitchy it wouldn't have the same impact on you now anyway. But, she may be sincere and wants to talk about the way she behaved - especially if she says she has feeling for you. I don't know, I think I'd be curious as to what she'd say (keep your heart guard on though) and then evaluate the situation. If, however, there is no way you want to be friends (or more) with her then just tell her that you are not going to be able to meet with her and leave it at that - don't lower yourself by being rude.