Mary considered that for a long time. She could have said Because I've done things I'm not proud of, just like you have, and I can't keeping hating you for what you did. She could have said I watched a man die and didn't try to stop it. She could have said It's not my position to keep judging you.
"I don't know," she eventually said. "I'm exhausted from holding onto this grudge and coming to realise I'm not the good person I thought I was anyway. What right do I have?"