No offense but with the aggression she is showing she does not seem like she would be a great specimin for breeding. Breeding should only be done to improve the breed. You want the parents, grand parents, great grandparents to be of great lines, all to free of any health problems, excellent health (tests etc.. to prove it), good standard for the breed, great personalities, good behavior and so on.
Spaying her may not only help with her behavior but will also make her healthier in the long run. It will reduce her chances of numerous cancers and infections by quite a bit.
And the sooner the better!!!!!
Granted spaying will probably just make her more focused on you the training, it might help with her aggression towards male dogs, but it will probably worsen the aggression with female dogs.
It is proven that spayed female dogs have more aggression towards each other than any other combination of sexes spayed/neutered or not.
Good luck