I totally agree that Arabs are really smart, and notorious for being dramatic not because they are necessarily scared, but because they know it gets a certain reaction out of someone. I worked with a mare that I knew wasn't handled right, so I assumed her "panicked" flying around her stall was her being scared. Found a rescue for her, and the guy nicely corrected my thinking. She wasn't scared at all, no matter how dramatic she was acting, And she was acting dramatic, she was flinging herself into the sides of the corral, and all the trainer was doing was standing in the middle not moving. She never broke a sweat with all that flying around. He said if she were truly scared, she'd be sweating almost from the get go, but she had just learned that flying around the stall made everyone leave her alone, and earned her the nickname of Crazy Alice.
You can't coddle a horse, sure you can give them some love, but even if she was abused early on in her life, she doesn't think "oh I was abused, I must be treated differently" all she knows is that hand near face normally means she must react, so she does. If you work with her with the mindset of "maybe she was abused, I must be really loving, and give her a few concessions with some behavior", she'll definitely get your number, and she won't ever change. I know that you were just looking for possible causes, so I'll just stop here with the training aspect.
Being head shy like that can happen for many different reasons. Her being a halter horse, it may just be habit now that hand around face, she must tense up, and throw her head up, or she may have been smacked in the face as a reprimand when she misbehaved. Or she's got some sight problems, and to her the hand near her face, or the bridle coming over her head is sudden even if it isn't. And the list goes on for possible causes. But the cause doesn't matter, what matters is that it gets fixed so that people don't get hurt working with her. I've had horses I've been working on space with, or bridling with that are reactive end up smacking me in the face with their heads when something startles them, and that's just when I'm standing getting them out of my space, there is a huge probability that you kissing on her face is going to result in you getting knocked out, nose broken, or some other injury, so please be careful.