I have figured out one thing today--when Crazy Sister started spinning out and getting all manic, I asked her about herself-- how she was coping. She stopped freaking out and told me all her problems. Then she was a lot more reasonable & rational. For today, anyway. She is very manipulative, has a ton of mental & emotional problems and takes it out on all of us. I think she can't handle not being in control or not being the center of attention.
So if I can't get her to back off, giving her the attention she wants will redirect her to something or someone else
In theory.
I have a sister-in-law exactly like that. She is the youngest of 4 kids and expects to be catered to all the time. She used to manipulate my husband all the time into giving her money. But, since his death 3 yrs ago, she doesn't have my phone number or any way to contact me so that's kind of a relief. I'll probably never know if she's alive or dead and I'm ok with that.