Regrading fear for picking up feet, I don't mean afraid of YOU. It couud be that she is afraid of the vulnerable feeling a prey animal has when it only has three feet available to it. That's what I mean by fear. Or, fear of losing her balance, believe it or not. Not fear of you. somehow you have to show her that she can have one foot held by a human and she will still be safe AND it won't last unbearably long. And you won't drop her foot or pull her off balance.
In the round pen if she is running into you, THAT might be a respect issue. there is where you may need to lay down the law a bit more strongly. I mean if she starts to come in to you uninvited (and if you are backing away from her, you are inviting her, so don't back away), then you swing the lead rope or smack the ground with a whip or shush the whip in front of you , whatever it takes to surprise her out of that zombie mind set of not seeing you as important and just running right through you. You have to maybe startle her enough to make a lasting impression, even to the point of laying the whip or rope a good smack on her neck. Her running over you is quite a serious infraction and must be met with an equally serious correction. Do it good once and you wont' have to do it again.
If you are asking her to back and she does something else, she either doesnt' understand or has , again, a physical issue. If you stop asking when she shows her confusion by doing other things, then you teach her that there are a multitude of responses that get you to leave off the pressure of the back up cue (wiggling the rope?). She rears, you stop. She goes left, you stop. She goes forward, you stop. You have taught her many different ways to get you to stop, except the one that matters, BACK UP>. So, don't , don't stop asking until she does the right thing. maybe only a step or two, but THE thing you want, then you stop.
Her running over you and her not backing up off of pressure are closely related and when you get her to not run into/over you, you will find backing up gets way easier.