I have dealt with people with borderline PD. Yes.

Of course not are all the same, but the ones I know share black and white thinking, blaming others for everything and complete and utter unpredictability. You seem to never ever know what comes next with them. You can’t fix them. And you can’t make them see things any different way.

They can get better if they work hard on themselves. One in my family has been improving. Not significantly enough but certainly has been doing better.

The last time she has been estranged from us for about a year was all because my husband suggested in a most loving ways that we reschedule our visit to her house because at that time she lived two hours away and was asking us to drive see her for only one hour as she had other plans. When he suggested we maybe move the plans to another day when she has more time, she possibly perceived it as a rejection and started screaming the most horrible obscenities. He tried to interrupt saying we will come but maybe like next day whenever she is free but she just screamed and screamed and then cut contacts. But when she decided to resume contacts she acted like nothing happened. She’s been good for the past year or so but we always wait for the other shoe to drop.

As about telling you to sell your stuff and move with her that’s weirdly common too. The one I am talking about convinced her mother (sadly also diagnosed with BPD) to sell all her stuff and move in with her. She did but it only lasted a few months, they got into a fight and she kicked her mother out like literally on the street. So moving in with your sister would be dangerous and will only last until she starts acting badly again. You might end up on the street or homeless shelter. No thanks

I’d say sending a card or calling with happy holidays is s good plan. Show your love and see if she can behave. It’s up to her to try acting better. You can’t fix her. You can still love her and show your love from the distance

You mentioned they typically alienate and cut contacts with everyone. Both family and friends. The one I mentioned lost all of her friends and in the family she only has contact with me and my husband. No contact with anyone. No friends and no family. Always over some type of real or perceived exaggerated drama, everyone is always after her.

PS I incorrectly assumed your sister has BPD. I misread your post. So people I am talking about one was actually diagnosed and the other was told she has traits. So it might be irrelevant but from from you describe it sounds she might have it. Or if she doesn’t have BPD, it might be something else similar to it. Bottom line there is nothing you can do. Nothing