It sounds like a power struggle to me and the usual toddler testing the boundaries behaviour.

We have a very strict rule around here, Mummy and Daddy do not listen to whinging. If DS asks for something in a demanding or whinging manner (eg repeating the same thing over and over) I insist that he stop, ask politely and wait for Mummy to respond. I am very strict with this, I can't stand whinging and it didn't take long for him to start understanding. I make sure I give him heaps of positive praise when he uses his manners and ignore him if he is whinging. If it is getting out if control, I tell him he can sit in his room until he can use his manners (no more than 2 mins) and it always works.

I think what your DD is doing normal toddler behaviour and I know how frustrating it is.

HTH
Spring