I vote for being a brat on the horse.
She has learned that you are not the leader, she may give in to you in a more enclosed area, but get outside that? She is running the show. And you don't seem to want to understand that.
I guarantee you, if you were truly the leader here, she would be fine. You aren't, so she isn't. This horse has no respect for you at all basically, and all you are doing with her is making it worse.
And have to wonder about the "trainers" too, if all they see if a "fearful" horse, and not a brat. It may also be too, that they think horse is spoiled, but know that isn't what you want to hear, or that you argue with them, so they don't say what they think.
If you can't afford a trainer, then get rid of this horse, as she has got you buffaloed, and you will shortly not be able to do anything at all with her. And if your handling has caused much of this, which I feel like it has, then don't get another horse, as it will end up like this too.
Your horse handling skills are lacking, and this horse is showing that clearly.
Horses make me a better person.