When it all goes seriously wrong

I'm really really sorry this happened to you. I can't imagine going through everything you did (you are very brave by the way) only to have your partner turn around and do this.
I hope you will continue doing what's right for you and your children first and foremost. This young woman cares for you but doesn't have the years of experience and responsibilities behind her that you do. The stakes for her are relatively low, or they were until it was getting close to her coming out to her own family. It's no coincidence that that decision was bearing down on her at the same time the travel plans suddenly popped up.
I don't know what you should do about but I think putting yourself first is a high priority.