[Tom4784]

Yes and no, You've every right to be upset but I don't think it's right to show any anger towards your friend or ex. I'm guessing both were single at the time so neither did anything wrong.

If I was you I'd talk to them both, find out if the friend likes the ex in a serious way and vice versa but also look at your own feelings. Are you mistaking wanting a reconciliation for closure? If you want to get back with your ex then talk to them both and make your intentions clear. If it's an issue of Closure then talk it out with your ex and try to move on.

All options lead to talking really, evaluate your own feelings before talking to any of them though.