Help me with my three year old please!?

First of all, you shouldn't yell at her if you want her to set a good example. I think that the best way to make your child to behave is to be calm, but firm. You should show your child that you never loose control of yourself, but you are in the charge of her. That will be a really good example, that would lead her to thinking that this is exactly how your child should act as well, since her mom(you) does.