Es,
I have seen similar situations to this more times than I care to remember. Your mum seems to acting like most jw parents do when their kids grow up and leave the org. Many of them feel let down by their childrens actions, and because they then have little or no influence over the choices their kids make they resort to emotional blackmail, something that most dubs are experts at. I've known parents who have told their dfd or da'd sons and daughters that their actions are tantamount to sentencing their own kids to death unless they alter the course they're on, and feel no apparent remorse at saying such a thing.
I would imagine that your mum is a caring person, but first and foremost she is a brainwashed jw, and will thus be inclined to look at things in the same warped way that most other jws do. I don't blame you for being pissed off at what is being said, but it's typical dub behaviour to blame everyone but themselves when things don't go the way they think they should. It's an attitude that permeates the whole religion, stemming from the gb - when do they ever apologise for anything they get wrong? I used to be just the same when I was in. I'm not in any way defending it, in your situation I'd be angry as well, but I doubt your mum can help herself really.
I agree with what another poster said - the best thing you can do is bring up happy, well - adjusted kids who are a credit to you and your husband. That would be the finest answer you could possibly give to your mum and her jw cronies. When they see that happening, it might just make them think a little.
love
Linda