I thought it was a complete challenge raising my kids when they were 3.
I knew in the back of my mind that they already had me figured out.
Also, kids at age three spend at least 1/2 of their time in the "testing" limits at home during this stage. Plus, alot of social/emotional growth is taking place now !
If she hits (which is common)...Pick her up immediately and tell her that hitting is not ok. Tell her it's ok to get mad but she can't hit people.
Some parents tell their kids to hit a pillow if they are mad. That did not work in my house.
A parenting expert once told me that if you are a wishy washy parent during the testing stage---which is usually age 3, then, put a number one in front of the 3. Why? She meant that if you were a push-over parent when the kid was 3, then, 13 would be ever so more difficult.
This bit of advice was especially true w/ kids who had "spirited" personalities.