Even if she had given up after a while, it would have been too late. The more time passed, I bet he would've wondered sometimes about her. He was already lonely from the start even if he was hurt.

Well... everyone hurts each other sometimes. That can't be helped. They'll probably have fights and she'll probably feel a little guilty always. He'll probably sometimes think he should've stayed in the dark. But you can't smile the same or feel as happy alone. Those memories mean more than any of the pain.

You said she was happy but lonely. I bet her smiles are a lot brighter now with him. I bet he didn't smile alone in the dark. That's how it is.