Albert69, I see where you are coming from. I’m sorry that you went through this. Your story is sad.
There is a line from the movie Braveheart where Mel Gibson says in response to an overture to speak to the nobles that his lieutenants clearly sniff out as a ruse.
Wallace: “Do you know what happens if we don’t try?”
One of his Lieutenants: “No what?”
Wallace: “Nothing”
OK, so maybe this is a poor example because Wallace ends up losing his head, but his death does effect the changes he wanted.
Nonetheless, for the OP do you know what happens if she does nothing?
Nothing happens.
Even your parents took the risk in trying because they had hope and at least wanted to effect change. You are suggesting based on your single experience that OP shouldn’t even try. That she should give up all hope. That she risks making herself vulnerable and having her adversaries stick it to her.
Therapy doesn’t help all of the time, but if it didn’t help some people, do you think therapy would even exist?
Don’t you think that’s it’s worth a shot?
Do you think that your parents regret trying to reconcile with your sister through therapy?