- Yes, it's bad
- No, you were single
Most Helpful Girl
If the relationship ended, then you were single. It's absolutely none of her business what you do. I would stop talking to her.2
Most Helpful Guy
If she left you, my opinion is that you had no responsibility to be faithful to her any more and she can't reasonably expect that.
Perhaps what she was thinking was that it was bad that you could so quickly sleep with someone else since that means you don't need/want any relationship before having sex with someone.1