I tend to think that as well as the changes at home you could be just dealing with the 'terrible 3's. Terrible 2's aren't much in comparison.

I'd say whatever you choose to do keep it consistant.

Set you boundries between both parents so you both accept and don't accept the same things.

I agree that a week is a long time when you're three, what you could possibly do is from now when you see behaviour to praise give a toy back one at a time or definately acknowledge it in some way.

I know with me i also found that i was saying 'no' to things that DS was possibly now quite capable of doing to a certain extent. Maybe you could start introducing a few new things that make her feel special, like a big girl. As they grow you often need to adjust the boundries that you set.

I know that kids can definatley have difficulting in dealing with change and act out in protest but as parents we always find a way to blame ourselves for things that may not be our fault. Maybe it's not so much a protest to change but just her being 3

Another thing that helps immensly is to not get worked up and yell when they do, keep your response calm (even when you are fuming inside).

It's tough but i promise you will see the results next year, DS1 has been so good of late... until the next 'stage'.... which i'm sure it's too far away