Call the trainer for the Schutzhund club and talk to them. It's not about making her not aggressive to other dogs. She will probably always be dog aggressive, though it seems odd to me that a 4 month old would be so is it maybe fear related? It's so hard to say when we haven't met the dog. So call the trainer and discuss with him. There are many working dogs out there that do not want to tolerate other dogs. They are trained to ignore them.
~The strength of one's opinion should not exceed their knowledge on the matter~