100% the boss was fishing for an excuse. Unless they're buddy buddy, you don't randomly ask about your superior's performance without there being an ulterior motive.

I'd advise against contacting her anyways. She's probably looking for a job now and picking up the pieces and there's nothing she can gain from being on good terms with OP. The trust is broken even if OP wasn't malicious considering now he's known to superiors as a blabbermouth.