She got upset because I flirted with another girl. But she cheated on me 3 years ago?

[Elsie]

Your ex is immature and you are well rid of her. She should have told you before the party that she wanted to try again, but she didn't. If she had, you could have told her privately that you weren't interested, she could have not come to the party and this entire situation would have been avoided.

The friend is just being a good friend...she doesn't want to upset her more by pursuing the flirtations with you. For future reference, it's never a good idea to hit on an exes friend unless you've talked to them first and they're ok with it.

If you're friends with the friend on facebook, send her a message saying you're sorry and explain how you had no idea the ex was interested in getting back together, so she knows you weren't just flirting to piss the ex off. If she's interested, she'll make the next move. But don't go chasing her. If she doesn't respond, let ti drop.

You might want to message the ex too, and explain that you weren't trying to make her jealous or mad, but you're sincerely not interested in trying again.