Disengaging from Adult SKs
I was rereading Captain Awkward's post about siblings, "Advice for Relationships You Dont Want To Lose But Dont Want To Work At" (#1182, #1183, #1184 3/4/19). Some of her advice applies to troubled adult SK relationships.
One excerpt that rang a bell with me:
"Adults are allowed to make choices about people that are informed by how they treat us and not everyone deserves our trust, our attention, our time, our focus, our benefit of the doubt."
She advises putting these folks on an "information diet" (minimizing info about our plans, opinions, etc). She also says you can forgive without forgetting and you can have empathy without taking on their problems.
I think the basic message is: polite and civil boundaries.