It comes up a lot in threads here where someone wants to have a friendship with a former romantic partner. It never turns out well. It always leads to hard feelings on someone's part.

When a romance is over, it's over. Both need to let go and move on. That's what the therapist should encourage. But you can't control all this dysfunctional behavior. All you can do is try not to feed in to it. It will all resolve eventually. You don't need to fix all this stuff. Just step back. When your friend wants to keep talking about these former relationships, try to be kind, but don't act too interested. It will just wear you out.

Your friend is fortunate to have you caring so much.