It was an angry retaliation. But firstly, I don't think it was as bad as you are making out, secondly I certainly don't regret it, because no such regret has ever been demonstrated by the other party. Why should I care about her feelings when she clearly doesn't care about mine.
The last time I made any effort at moving on and forgetting the arguments, I got an angry retaliation in response. So I don't think I'll be making any more such efforts.
And I'm very sorry you feel that way. But sh*t happens, I'm sure I will get over it. It's not like I was highly likely to see you again anyway. Disappointing, but that's life.
Genuinely sorry you put your pride above friendship. But I suppose that's your call.