From your description, it sounds as if there is any love involved, then that is not "respecting" their relationship.
If this is true, he will eventually realize it - if he hasn't already. What gets done about probably will be determined by how they are as a couple. If she can't handle it, and they can function as mono, they could close the relationship. But if they cannot, and she can't overcome her insecurities, this will eventually become unsustainable.