
They are very good but like so may other ways of training a dog, timing is of the essence. Have used a Master Collar on any number of problems with much success but never on one of aggression.
Only you can see the situation and know if it is true aggression or her OTT way of having fun, would try it but be quick and never use it when she is near other dogs or horses. She could blame the other animal for the shock and attack. There is also the problem that the other animal may be startled too and if it is a horse that is not a good idea.
The first time I used it was to stop one of the dogs jumping onto the windowsill and shouting at passers by, I got the timing wrong and fired it when he was on the sill, it worked, stopped him barking out of the window, stopped him going onto the sill, in fact, stopped him going to that side of the room. None of that mattered but you see what I mean timing is important. If I am within earshot I call
no and when ignored I fire the collar, it only takes once or twice and they know that no means no.