Friend, I and friend's DP all met at the same time around a year ago (we are all mid-20s). At the time when they were just getting it together I tried it on with him. I don't know why, I was going through a shit time but that's no excuse. I have apologised to her, although she has every right to tell me to fuck off. I don't know what to do. I can't undo it, I feel awful and so ashamed/angry with myself.