I have worked with a lot of horses with problems like this. I have found what works best for me is to get them in the round pen. Teach her to stay out of your space while she is working. Only let her walk towards you when she stops when you give her the ok. When leading, practice walking her with your arm out to keep her a distance from you. If you are standing still and she nudges, make her back up. Then let her move up a few steps again and if she does it again, back her up again etc. She will eventually learn that if she is going to be pushy, then she will have to move her feet instead of being able to stand. thses things have helped with my horses, hope it works for you!