I think my sister has BPD... now what?

[mrsmick]

Sorry in advance if this is lengthy. I am a 37 year old female and my sister is 41. As long as I can remember, I have felt like the "older" sibling (more emotionally mature).
As a teenager, my memories of her are of her being depressed and acting out. Doing drugs, sneaking out, that sort of thing. Which, I know, sounds like a normal teenager. But she would get violent with me, hold me against the wall, that sort of thing.
As adults, its pretty much the same, acting out...just verbally, not physically. I don't know if I can name one friend she has that she has an always constant relationship with. She has had friends in the past, "best friends," and they are here the one day and gone the next, and she has nothing but NASTY things to say about them, and what they did to her. I never remember her having a good relationship with my parents.  
As an adult, the talk about "everything my parents did wrong when she was a child" continues. (I remember a fairly benign childhood, nothing traumatic, just the episodes which involved her. I remember her walking down the stairs with a glass bottle telling my father if he didn't let her go some place she wanted, she was going to slam the bottle against her head.)
She's married, with twin boys. We live about an hour apart, and I feel like, even though I attempt to call/text her randomly to catch up...she won't pick up my calls unless she needs me to be her sounding board. Also, she won't call or text me for weeks until she needs someone to hear her vent about my parents, her husband, etc.
The latest (and biggest event) was my brother in law being diagnosed in the summer of 2017 with Leukemia. He has been through countless chemo treatments, a bone marrow transplant (his body had a very very tough time with this), a relapse after the transplant, more chemo, another donor cell transplant. And finally got word last month (2/19) that he is in remission. I remember one of the first things out of her mouth after he was diagnosed and they talked about possibly 5 years of chemo, was how this was going to affect HER life and that its "going to be 5 years of the (husband's name) show." Over and over the past two years, she has made comments like this. Basically acting as if he CHOSE cancer, and that him "choosing" to get cancer is ruining HER life, and the fact that "she basically has to raise the kids by herself" (for that period in time). Everything in their marriage is HIS fault, according to her. My brother in law is one of the most laid back people I've ever met and I am surprised he has dealt with her this long. Everytime something goes wrong, she wants to point the finger at someone else, never herself. Even her boys (they're 6) have taken on some of these traits...if something happens to them (they get hurt, etc.) it's ALWAYS someone else's fault.
I know this is a lot, sorry if its rambling. I just don't know where to go from here. Everything in her life is my parent's fault, everything in her marriage is her husband's fault, she changes at the drop of a hat. I just need some solid advice on what I (as her sister) can do next. To move forward, to help her move forward.  

[Woolspinner2000]

Hi mrsmick!

Welcome!  It's great to have another member join our online family.

It sounds as if it has been quite the rocky journey with your sister, and I imagine you have had a time of dealing with fear based on the way she has treated you. My uBPDm was very similar in her dealings with me, and no matter who the person with BPD, it is a tough road.

The blaming of everyone is a classic behavior of someone with BPD. The struggle to self sooth, especially after rejection or perceived rejection, is so strong and they find a certain comfort in eliminating people from their lives because they're very black and white. We often refer to this as Splitting, making people either good or bad. Does this ring a bell with you?

I hope you do something kind for yourself today or tomorrow. It's important that you care for you and your soul. You have been deeply hurt and can use some extra special care of YOU! Please let us know more of your story.

 
Wools

[Turkish]

Those are  things to say given what your BIL is going through.

Even though you are fond of him or love him as a BIL,  their relationship is theirs,  as messed up as it is due to her self-centeredness.  You can't fix that,  as frustrating and even hurtful as it is.