Horse becomes a total jerk when people show up? Idiot horse people ruining training.?

Is there a chance you could round up a few "makeshift girl scouts" to stand around, being goofy and excited, carrying treats? You could practice doing lots and lots and lots of groundwork with your "girl scouts" nearby being distracted, until your horse realizes that just because other people are around doesn't mean she can be rude and stupid. What is happening right now is that she's turning off her brain in the presence of potential treats and hugs, and isn't even thinking about her manners. You need to teach her to listen to you no matter what her surroundings are. If you can practice this regularly, hopefully you will see a difference.