Update:

I took your advice, and for the last 4 months avoided any kind of involvement in my sister and mother's personal lives. I still talk to them, but only about general stuff, books and movies, the weather, etc. I have NEVER felt better! I feel healthy and sane again. I don’t want to jinx it, but I have not been triggered even once in 4 months!

Thank you! Thank you SO so much!! You guys have been really helpful! Big hugs to all of you!!