So, I've been seeing someone with BPD for 4 months now, and so far, so good. We'll call them 'Pat' for the sake of conversation. I feel like I understand the situation and handle it appropriately. 

However, that's only when it comes to us and our relationship. Pat has been complaining a lot about their parents recently. Pat feels that they "cannot get a word in" and feels like their privacy is being invaded consistently. I know Pat's mother, and she does have a tendency to go on and on and make themselves a part of the conversation at inappropriate times.

It seems like this situation is making Pat's condition much worse. Pat is very good when they're away from their parents but often seems agitated and shorter fused after spending time with their parents.

I'm maintaining medium-chill and using SET to defuse potentially explosive conversations.

I'm not sure how to handle the situation and would appreciate any advice you all may have.