I don't know that it is your place to help her in her relationship with her children. Every counselor I have seen has said to let him manage his own relationship with the children and not to help or enable him.
She has to face consequences for her choices and she has to learn what it is to live a Gordie free life. Certainly if you see the disrespect when they are with you, you should correct. When my children say nasty things about my H I tell them that it is not appropriate for them to speak about their father that way, regardless of how he is behaving. Two wrongs do not make a right.
I would politely tell her that you will correct that behavior if you see it while you are with the children and that you are sure she will do the same. You are correct, they don't respect her, they likely don't trust her, and if you don't stay out of this you will negatively impact your own relationship with the kids.
