If she's pushing you around, you're going to have to get firm with her now or it will just get worse. Momma donk will put up with so much crap from her foal & then she will bite or kick back to tell them to knock it off. YOU are now Momma donk. A quick slap on the neck is not going to hurt her. A very loud "NO" will back up the idea. Mini or not, bad behavior is bad behavior. Horses try to go away from pressure. A donkey will push back. Pushing her will not help, you have to let her know you mean business.
In donkey play, biting on the neck is common. It looks horrible, but it's just what they do. The older donk is probably just putting up with baby & will tell her when enough is enough.
Get "The Donkey Companion" by Sue Weaver. It's been my "go to" book for donkeys.
I agree, which is why she chases the truck, because you're in it. Clicker training to stay within a certain area of the pasture when you leave would be a great way to teach her to not chase you when you leave, and it would be a loss stressful for her as well.
I have videos at home of a miniature we bought years ago who had a similar issue and we retrained to not behave that way. It was quick and stopped the issues. You definitely to work in fixing that now why it's just the beginning of the behaviour, before it becomes a more permanent that will be difficult to stop. Ill repost when I find the video. Posted via Mobile Device