Coincidence or no? How to handle this situation

Okay so this story may sound a little weird, so let me just start off & give some background. I’ve been with my fiancé for 3 years & we have a 6month old together. My fiancé is bisexual, and has also been diagnosed with HIV before me, but his status is currently undetectable. He was honest about everything from the very beginning, and I respected that. Now, I’ve never shared any of this information with my family because it’s none of their business. Plus, they all have their own hang ups about gay people so I just saved myself the headache of dealing with that.

Now, on to the problem.. My mother is bipolar & lately she’s been showing signs that she’s off her medication, so my fiancé & I took her to the hospital. While she’s having her episodes in the ER waiting, she kept YELLING in the hospital that my SO is gay & has AIDS. It was so embarrassing. I understand that she really doesn’t have control of herself when she’s like that, but I’m just concerned because how does she know that???? We’re very private & I can’t possibly know how she’d know. My SO said it could all just be a coincidence, but idk... it just sounds too spot on for her claim to be random, you know?

I’m trying to decide how the heck do I go about this... when she gets better, should I ask where she heard the information, or why she thinks that? Or do I just leave it alone??? He & I both are still against disclosing his personal information with them so I just need help on how to move forward. Any suggestions would be helpful