Yup, sounds like you have to take charge, as long as dck is in your vicinity. She will learn....
I have it stated in my handbook that when they are picking up/dropping off, THEY are responsible for the child's behaviour and THEY are expected to enforce my house rules. That being said, the day that a dck kicked my front door because he didn't like something his dad said; I took over!!
They will treat their parents in whichever way they are allowed to when not around me. But don't even think about doing that kind of crap in my home.