@TheCheekOfSomePeople I told them that every time there is an absolutely ridiculous statement in front of me, my official response would be to blow a raspberry. That's what I do! It's been a few years now and everyone laughs. It shuts the conversations down though.
And she does try to manipulate my DH by saying that I don't make her feel welcome (so very untrue, she has so many requirements for her visits, I have to prepare a lot!) or when she is making snide comments which are not an open demand or a direct criticism, such as 'I don't know why you won't give the children cordial to drink, I mean, what are they supposed to drink?' or 'DH never ate this many vegetables when he was a child', I respond along the lines of, 'I know, but I just feel that water/vegetables is better for them and I want them to enjoy it. It's nice to keep cordial and juices/chips for a treat, don't you think?' And smile.
She struggles to continue with the criticism when I am killing her with kindness...
And when she does things like you are dealing with, I am not afraid to be the bad guy. It is not DH's fault that she chooses to go through him and she is such a force that he finds it hard to shut her down. He is kind and trying to be respectful, but she is incredibly difficult and loves to play the victim. (For example, when DS1 was born, she planned days out, with just my newborn and her. DH day her down and actually said 'he's EBF, he can't be away from Sally, plus, he's a tiny baby, she doesn't want be apart from him.' She regurgitated it (and continues to do so) as Sally wasn't comfortable with me having the baby. And that is what she told people... he could have gone back in there and corrected her but it would have added fuel to the fire, and quite frankly, we had other things to put our energy into.
I've developed a thick skin over the years...
Also, minimum contact. Not no contact, as that would be construed as rude, but definitely at a minimum.
Plus, she has another DIL, we are close and can rant away to each other. This is a real help!