Any direct communication of remorse would've sufficed. I readily apologize when I make a mistake--including for mistakes I've made in regards to the woman in the story. Everyone who I've ever been in a relationship with before this woman would apologize when they made a mistake.

Apologies, saying I'm sorry, expressing remorse, promising not to repeat the action, doing what we can to make it right, etc., are very normal human behaviors that allow us to move on from past mistakes. I don't think it's too much to expect from a person.