So-Crafty, it sounds like that technique is geared primarily towards fear aggressive dogs. It's mainly attempting to replace a dog's negative connotation with something positive. That's the standard treatment for a fear aggressive dog, but, IMO, it will provide minimal lasting effects for a non-fear-aggressive dog. From what Erika wrote, it doesn't sound like Jemima has classic fear aggression and that she needs more intense training than mere counter-conditioning. Jemima's radical shift in behavior is indicative to me, at least, that she has more problems than fear aggression. These are the issues I see:
- She doesn't provide ample warning signs. Normal dogs growl. Dogs who skip growling and go straight from staring to attacking are the more dangerous with which to work. Erika wrote that she couldn't detect any obvious change in body language. That probably means Jemima gave a quick 1-2 second warning of hard eyes, tense muscles, staring, etc. before she struck. In other words, it was all silent and almost indiscernible. That's dangerous..
- She has a low threshold and low impulse control. Both of these can be raised, but it takes time and a lot of training.
- She needs very concrete rules and guidelines.
- She needs structured, supervised socialization opportunities that focus on her ability to focus on the handler in the presence of other dogs. So, basically, she needs to learn that other dogs are no big deal, and this requires more intense training than counter conditioning.

It's not an easy task, and I extend all my hope, help, and thoughts to you, Erika!