Thanks all. I have probably been down-playing her behaviour because I'm trying to think positively but she did try to maul two puppies at pre-school, the trainer had to yank her away and then she turned on her (and drew blood).
The fear aggression was mentioned by the animal trainer (who has qualifications in animal behaviour), it's not something we have said for no reason. I've never in my life seen a dog try to maul other puppies (the same size) when they haven't done anything. It was very alarming.
I spoke to SAFE on the phone this morning and they are getting their animal behaviour expert to talk to us to see what's the best solution. Jsut wanted you to know that we have never (and would never) hit her or yelled at her. We just use a firm voice and single word commands. But when she's in one of those frenzies she doesn't listen to anything.