Oh, the whole way through "Smaug", I was running VERY unflattering commentary in my head. It was all I could do to restrain myself from screaming "NOOOOOOOOOOOOOOOOOOOOOOOOO!!!!!!!!!!!!!" and running out. I very nearly left several times, but had hubby with me, so didn't.
Magpie - next time your mother undermines you, say sternly to her "NO! In THIS house we go by the parents rules. You are not to undermine that, ever. You are not raising this child - we are." Then go on with activity, and ignore any attempt to engage - simply repeat "we have our rules - you don't get to change them."