TLDR: I have fighting adult siblings. How can I mediate?
I have two adult sisters (I'll call them Janet and Carol) who have been fighting for some time now.
The root of the fight was two years ago when Janet lived at Carol's house. Janet was in a very unfortunate situation and needed help. But Janet began to take advantage of Carol. Eventually Carol put her foot down and called out Janet for her behavior. Janet moved out and and hasn't forgiven Carol since.
From my point of view Carol has reached out a couple times to fix the relationship and apologize but Janet rebuffs these attempts.
This is where it feels tricky. Our family will still hang out with both Janet and Carol (though not together). Carol feels a little hurt that it feels everyone is condoning Janet's behavior - which is somewhat true. As they are both adults it feels awkward to call out Janet. It's gotten to the point where Carol doesn't feel welcome anymore and is moving out of state.
I can talk to Carol openly about it. If I bring it up to Janet, or suggest she lets things go, she will become very cold.
It has had far reaching effects on all our siblings. If any kind of party is held, Janet won't come if Carol is there and vice versa. It is hard to quantify but this has caused great emotional anguish for my parents and other siblings.
What strategies can I employ to mend this relationship as a sibling?