So sorry to hear you are having these problems. I would definitely muzzle her for everyone's safety.
One thing I'd like to suggest as well is having her looked at by a McTimoney Chiropractor to make sure all is okay with her back. If a dog's Atlas is out (where the neck joins the skull) it can affect their vision as the optic nerves run through that area, and it can make dogs be more reactive because it affects things like their ability to recognise silhouettes (eg they may have only just seen someone and then they come back in the room and react as if it's a complete stranger). Back problems can have a big impact on behaviour as I know from Zorro - he may not show that he's in any pain at all but he gets very reactive to Bella (and alot of other stuff too) when his back is rickety so it's worth thinking about.
90% of the time aggression is triggered by fear but it can often be that a series of things have added up to the point where the dog reacts in this way (a bit like us having one of those really bad days and then going home, knocking a glass of water over and completely hitting the roof - it's not the glass of water that was the problem, it's the culmination of all the other stuff, so you need to bear that in mind - sounds like you are already though

).
It might be worth keeping a diary of her day to day routines so you can start to try and figure out what little things might be adding up for her. Hope you can get a good behaviourist and get to the bottom of it, it's a horrible situation...