You need to gear up and read Grasshopper's tale here on the boards. The OM is really not the issue, but he is a detail that will need to be dealt with.
You have begun to assert yourself. Don't let it explode in your face just because you caught her in a lie. Now is the time to anchor the feelings you've started to generate. You need to show her you ARE the best alternative. Continue now that you can see it's having an effect. Keep working on being the "best choice".
I see many positives and you need to keep track of those. Keep your true goals in mind. Your boundaries are important but sometimes you need to take a loss in one area to win in another. It's not a game but it is a plan. Keep improving and be the best person you can be and if she, after you look in the mirror and say "I'm the best I can be and have done all I can", still doesn't chose you then your conscience is clear.
