I'm more familiar with Rottweilers than pitbulls - Lucky, chime in here.
How about a pinch/prong collar? I know they can work wonders as a training tool for certain situations and certain dogs. Note I said training tool, not a substitute for training. I also realise that they can be counterproductive with aggression issues if the dog feels the pinch and wants to redirect at the other dog.
It did NOT work with Cooper; I've had him since 8 weeks old and used very little compulsion type training with him. I tried at at the urging of the trainers at a facility I was going to (they were jerks, when I figured THAT out I walked out one night mid-class in a snit.) Anyhow, it didn't work with Cooper and he got real grumpy and just refused to work; I haven't used it since.
The reason I tried it on Coop was he got real stupid about other males when he was an adolescent & I hadn't yet neutered him. General obedience and as many as three drop in obedience classes a week, around different dogs, helps desensitize him to other dogs. I'd definitely suggest lots of exposure to other dogs in structured situations, and not getting close enough for her to get real aroused until you can get her to pay attention to you.
But with Dutch (a dominant, very dog-aggressive, intact adult male I took in last year) using a micro-pinch was amazing. Like having power steering!
He is much improved now, but at first he just wanted to flatten every dog he saw and I could have been an ant on his butt for all the attention he'd pay to me. I credit the pinch collar for making Dutch a much better citizen.
FWIW - "Watch" is a great command. It takes time for a dog to get reliable about it, especially in a high distraction situation. I can tell you Dutch was not about to focus on anything except what HE wanted; I had to be quite a bit more forceful to get his attention.
One other point - getting her attention BEFORE she gets into staring and posturing at other dogs is most effective. It's 50 times harder once she's tuned you out and gone into drive over something.
I think I rambled a bit...it's been a long week!
So LR, do you think a pinch collar *might* be useful?
PS: Prong/pinch collars are more effective and less potentially damaging to a dog's neck, trachea, and spine that choke collars. I know they look like torture devices, but they are really more humane, IMHO.