What has worried me is that she will run off with OM while she is under the delusion that he makes her happy. I'm afraid if she does this she'll end up devastated about it further down the road. I don't want to see her do this to herself,
IMO, your statement above shows me that you think you can change her, control her, or that you need to protect her from her obviously BAD choices. Tough lesson to learn here --- you can't protect her, you can't change her. Especially when she is in the FOG, and still getting some of her needs met by you. She is making choices and she will have to deal with them one day. If she runs off to be with OM, then she will probably hate herself one day. But you can't force her to change. That was a tough lesson for me to learn.
I think you need to get yourself right. YOU can't change her feelings. Only she can do that. You need to work on you. The DB, GAL, all of that good stuff. Be a better you, and do it for you, not her. DO NOT DEPEND ON HER FOR YOUR HAPPINESS!
IMHO, the more you chase, the more she will run away. Be a confident man. Be a strong man. I doubt there are many woman who WANT to be with a guy who is willing to share their love. So don't share her.
Be strong, D&C. This stuff is HARD, but you can do it.
