Whether she's pregnant or not, her body thinks she's pregnant. When a bitch goes into heat and especially if she's mated, the body reacts as if she's pregnant--to the extent of a false pregnancy even if she didn't 'take'. Pregnant dogs and dams with pups can be very territorial and protective, especially against males. If she's pregnant, the aggression will likely get worse. Likely you'll need to separate her from the other dogs--at least until the puppies are weaned.
This is something you should have researched before
deciding to allow her to be bred. I hope you are researching now and getting her supportive veterinary care so that the pups (if there are any) get the best start possible.
Both dam and sire are too young to have been health checked--something else you should have looked into.
that the pups don't suffer in the long run for it...