This is a relationship that never got the chance to take off because this is a bad time for her. Which is what she meant by
"So I think it's best we both forget before we dwell on it"
She feels bad for leading the man to think that she's ready for a relationship. Which is what she meant by "Well, maybe I'm a crook for stealing your heart away
Yeah, maybe I'm a crook for not caring for it
Yeah, maybe I'm a bad, bad, bad, bad person". She's not ready for a relationship and she's trying to stop him before he gets to close to her.