I am glad you found this community, DL. Welcome!
There are many resources, tools, and support for you here. Your post shows compassion and love for your sister even when she is doing and saying painful things.
No time limit was discussed, I have a fear that left like this, it may be forever. Question: how to re-establish communication without feeding into the drama or is it even a good idea to try? It has been two weeks with no contact so far.
Would writing a brief email that keeps the relationship door open be a possibility? There is a book that the parents of children with BPD use quite a bit by Valerie Porr. I think the title is
Overcoming Borderline Personality Disorder. In the book are sample letters to write in order to reestablish communication. Many members on the parenting board have found great success with this written communication method along with patience, radical acceptance, and time.
Writing a brief email where you own your mistakes and that you are working on doing better and ending with a sincere restatement of love for your sister and desire for connection when she is ready is something that works for some members. Building such bridges does take quite a bit of time and emotional energy, and it can be two step stones forward, one step stone back process, as I'm sure you're well aware. We also have to be prepared that such messages are often met with angry and hurtful responses or silence from the other person. (I have had this happen to me a few times with my husband's sister. I continue repeating that it is not about me; it is about her.) You would let your sister know that you care and when she is in a less dysregulated place, she will remember that you reached out/wanted to keep the door open.
Does this sound like a possibility? I'm sure others will be along soon to welcome you to this group, too, and offer additional suggestions.