Actually, I think Mayflow is on to something, although I'm probably a little more lax about it since this is a discussion and not an attack on someone or trying to ruin their reputation.
If it's a question of etiquette. Then definitely I think tactful honesty is the best policy. It's just as rude, (in my opinion-more so), to be friendly with someone because of "etiquette" and then trash them later behind their back.
Uber, if you can forgive her and move on, I would. It's not worth the drama or energy. (Also, no offense intended...I don't think you're really trashing her right now by discussing this, just wanted to make that clear. Although, I must say I think it would be silly of you to be dislike someone because they disliked you in the past...sounds a little too much like grade school).