I think dp is under the illusion that she can do no wrong... Even when she has insulted something about me infront of my children.
You may have a much bigger problem than you realise.
If she is insulting you in front of the kids and your husband isn't seeing the problem or isn't reacting, then he hasn't got your back. In fact, the fact that she's insulting you is worrying, when you put that together with the digs about his ex - there's there possibility that you're going to have a lot more trouble in future with her.
Insulting you when your children are there is absolutely unacceptable.
I know this sounds harsh, but a man who is fully adult stands up for his fiancé when their mother starts pinpricking them. He's independent of her emotionally, even while he loves her. He certainly doesn't allow her to be insulting in front of his prospective stepchildren. It could be worth observing how he is with her with a detached eye for a time. If he puts you second to her in the marriage, you're going to have a battle on your hands and possibly a very miserable time.
All this may be extrapolating too far but there are definitely some red flags flying here. Also, you need action from him, not words.
This may be extrapolating too far