Have you thought about getting to know the guy that she's interested in? Sometimes meeting a real person can go a long way to defusing the imaginary threat or the bigger than human portrayal that your mind makes up about him.
Part of the difficulty might be that with another man there's the opportunity to make direct comparisons between you and him. Because you know you better than anyone else you're going to be able to pick out those omega characteristics in yourself much easier than anyone else would be able to see. At the same time you won't necessarily see those same characteristics in this other man. Therefore if you compare yourself with the information that you have you're setting yourself up to lose.
If you don't think you can handle a meeting in person right now try emailing back and forth to get an idea of what he's all about. Look for similarities between the two of you. Seeing something similar in him is a good reminder about what she sees in you.
Everything will be ok in the end. If it's not ok it's not the end.