YANBU, and honestly this is more confusing (and hurtful) than a clean drift would be. If she'd just faded away, that's sad but at least straightforward. But finding out she's still asking about you and your family, and criticising, while giving you nothing but "busy" and vague promises to your face, is genuinely two-faced — that's a betrayal, and honestly, some things like that just aren't forgivable once you know about them.
25 years, all the milestones you went through together, deserves better than that, and I think it's fair to feel more unsettled by this than by an ordinary falling-out.
On contacting her again to ask what you've done: I'd gently push back on that instinct, not because you're wrong to want an answer, but because you've already asked directly and been told "nothing's wrong" — going back again to ask "what did I do" puts you in the position of assuming fault that may not even be yours, when the actual issue is her talking about you behind your back rather than to you.
If you do want to say anything, it might be more useful to address what you've actually found out, rather than asking to be assessed again — something like "I've heard you've been asking about us and passing comment, if there's something on your mind I'd genuinely rather hear it from you directly." That puts the honesty question back on her, rather than you auditioning for what you might have done wrong.
But if it's landed for you as a betrayal you wouldn't forgive, that's a completely fair place to land too. You've tried, honestly and repeatedly, for years. You don't owe more chasing, or more forgiveness, to someone being two-faced behind your back while giving you nothing to your face.