When she's dancing around, dont get mad at her, instead put her back to where you want her, and tell her to stand in a firm voice, and put your hand up. When she moves, calmly put her back and ask her to stand. When you can tell shes thinking of moving, tell her to stand again. Eventually she will get, when you say stand, it means stand still.
You can also practice this before and after you ride. Have her stand in the middle of the ring, and ask her to stand, and walk around her. If she trys to follow you, you can tell her no, put her back and try again. Its better if you start this when there is no other horses in the ring, in case she decides to walk off. Pretty soon you will be able to stand her in the ring, and be able to set up jumps, trot polls or even be able to run into the barn to grab something (if you're like me, I always forget a crop).
It isnt really fair to expect her to stand still at feed time, I mean... its food! If its possible, let her stand in a stall until its over, that way you dont have to fight her stomache
If she trys to run you over, dont be afraid to give her a smack or a knee (whatever is easier, available). Shes young, so she will test you. One time I was braiding a 4 year old, and she decided to move sideways towards me, I didnt have any hands so I gave her a good knee in the side and told her to stand up. She was an angel after that, and got lots of praise for standing.
Dont be afraid to get firm with her, she's young so she doesnt know all the rules yet, but you can't let her push you around.