I didn’t receive any reply’s when I first posted this, so I’m hoping someone sees it this time. 

First of all, hello there everyone. I hope you are well and staying safe.

This is my first time posting on this subreddit. I actually don’t have BPD, but my partner does, and I am looking for some insight/advice.

About two weeks ago, me and my partner attended a get together at my sister-in-laws house.

Long story short, alcohol was consumed by all individuals and things were done and said between my partner, myself, her best friend and my sister-in-law. There was no physical violence, but the people that attended thought it was close between my partner and sister-in-law.

My partner more or less had a mental breakdown in front of our very eyes, and it was impossible to de escalate the situation. After all of the dust had settled, she decided to leave. Once she got home, she self harmed. She was in the worst state I have ever seen her in, and she’s lucky to be alive. I am very thankful she is okay.

Things were said by my partner that are difficult to come back from. She lashed out at everyone there - including me, but we have since resolved our issues. I try to understand her as much as possible, and like to think I do an okay job. I love her and want to understand, so we have made peace with that night and moved on.

However, my partner and my sister-in-law haven’t talked since.

The day after the incident, my partner needed some time to come to grips with what happened in her own head. Totally understandable. My partners best friend understood this - and gave her the space she needed. My sister-in-law, did not. She rejected the idea of this. She went on a bit of a tirade, and mocked her mental health, more or less.

She was angry at what had transpired that night. And rightly so, but the things that were said after that from her, were wrong and below the belt.

Long story short (well, long story long)
I would like to know what can be done to help them get back to a level ground?

They are both incredibly close to each other, and are almost as stubborn as one another. They both have genuine gripes - but refuse to conversate so the issues can be spoken about/resolved.

Does anyone have any advice for her?

Sorry for such a long post.