That’d be a sorry sentiment—holding onto a ring from someone who had humiliated her like that.
I think once any gift is given, it’s within the recipient’s right to do as he or she pleases with it. Perhaps she’ll find herself in a situation where she desperately needs the money for herself or a loved one.
Now, it actually might help her to reach closure and move on if she returned the ring to him, and that may be a noble gesture on her part. But I don’t consider it an obligation.
Some people, when they look back, tend to focus on the positives of situations. Besides which, humiliation would be if some other woman ended up wearing that ring!