The only thing I can think of that I do in your situation is avoid, try not to go there in my head and wait it out. There isn't much you can do with a metamour relationship that is not working other than strive to be friendly, courteous and respectful and stay the hell away from them for your own sanities sake. At least until you can breath through situaions where she is creating issues and drama out of her own stuff. Don't make more drama essentially. Its hard work, but I see it as working with someone I don't get along with. I have to do my job, but I don't have to like everyone I work with.
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