anyone any tips on a 6 month old gsd bitch who is very bright and quick to learn, but is very agressive (barking) to other dogs and strangers. We have socialised her from a very early age, shopping centres, car boots and dog clubs etc. We think its fear. Any tips. We have 2 well behaved dogs at home with her an she is fine with them.

Is the aggression worse in certain situations - is it in the house or out on walks ? We had a terrier some years ago who suffered from fear aggression. His main fear was the single dog/person walking towards him. Presumably you have tried the usual distraction methods - food, titbits etc ?
Do you use a halti - these do give more control.
Joyce