She has to recognize that the man is gone--as gone as if a truck had hit him. Even if he returns, he is gone from her and can no longer be a part of her life. She also has to recognize that she has behaved very unwisely. As you say, she was "too" in love--she had invested too much of herself in an asset that has turned out to be a bad risk and eventually a major loss.
Now she has to find new interests. Not knowing her, I cannot tell what they might be--reading, music, appreciation of nature, volunteer activity, church, or whatever is closest to her. She has to want these as a new life, not as stopgaps while she waits for him to return. These new interests will be more valuable to her if she can share them with someone. That is where you may come in. It would be better still if she could share those interests with someone she loves. That cannot be ordered up. But love is more likely to come if she is an interested and interesting person.
I strongly recommend that she read a little book by Viktor E. Frankl, Man's Search for Meaning. It shows what the will to appreciate and restore life can do in the most adverse of circumstances.