Yeah I think antlers is right. I think you are doing a great job on your GAL and it is yeilding some results. She is not right in the head and having a serious talk about your situation is persuing and it will not help right now. If you think she is cake eating and you have had enough, don't allow it. Don't go on the trip. (But I would want to if I were you...because of the kids). But you shouldn't act when you are spinning over something she said under pressure. She was confronted by your S and she said something that she knew would get him to stop. "don't believe anything they say"...
Continue to be better than the OM in every way. Be YOU. And you are the one who is there...I see that as an advantage over OM. He is just clouding her judgement towards you, and if you are willing to wait it out and see what happens, it may just fizzle out with him. That is what usually happens, so I have read here on these boards.
Hang in there...
Anything happen today?