Can't help but agree with Sandy. Treats would be extremely counter-productive here, if not downright dangerous.
Have you worked with her much on the ground? It sounds like she could use some serious lessons in respect. It might sound like it would only make her like you less, but it really wouldn't. She needs someone to stand up to her and put her in her place, a strong leader. You must become her leader before you can become her friend.
Especially in horses with this type of personality I would highly advise doing a lot of work down at her level, one-on-one. Does she lunge? I feel the impression that she wouldn't. If she does, does she listen and keep an ear on you, or does she look around and wait for something more interesting to happen somewhere outside the pen?
Solid, properly executed lunging sessions can do wonders to get that respect from a horse.
I'd also bet she'd benefit from some solid standard groundwork exercises, making her step over in the front and hind, backwards, forwards, moving her all over...and really making her move, as in "You will go how I tell you to go when I tell you to go or you will be made to go."
Exercises like that are what are really going to build the foundation of your relationship with your horse, believe it or not. My mare was almost just the same way when I started working with her, but now she's ecstatic to see me and follows me like a puppy. She just needed to learn that I was to be respected and therefore could be trusted. You really must think like a horse when it comes to these things...and let's just say a submissive horse would most definitely not be caught behaving that way towards her leader!