Have any of you ever had a friend whose partner you may suspect has undiagnosed BPD? 

My buddy and I have been friends for a decade (we're both in our 30s now). He and his wife have been together for about 5 years. He's a really cool guy; kind, patient, and never says a bad thing about anyone.

There have been times when I've gone over to his place to hang out. I'm even friendly with his wife and I like her well enough. It's been pretty chill for the most part, but she's demonstrated a few traits that could be consistent with some type B PDs (i.e. thinks relationships with certain people are more intimate than they are, overly dramatic at times, cannot stand being alone, mood changes on a dime, history with trauma--all this she's either told me or I've observed directly from our limited interactions). She's open about being bipolar, but I'm sensing there may be something else going on.

While my friend seems to be a caring and devoted husband, I'm concerned because he tends to want to bury his head in the sand about things. He also seems afraid to displease her (not that I suspect any physical abuse, but more anticipating the emotional labor than anything). They're planning to try for a baby soon, too.

Maybe it's none of my business and I'd be way out of line for reaching out to him about this (or could be that she's already diagnosed and in treatment), but I'm conflicted. I'm coming from a place of compassion for him and his wife. My intention would be to just bring it up to him once, stay factual and compassionate, keep it short, maybe get his thoughts if he's open to sharing, and then drop it. From what I've read, BPD can be very treatable with DBT. And I know a person doesn't need a diagnosis to be dramatic or manipulative, but if it's not something they've considered then it could be a missed opportunity.

Any thoughts, advice, or similar experiences? If it sounds like I'm about to stick my nose where is doesn't belong, please tell me.