It's hard to say if it's dominance or aggression without seeing it happen. It could also be that she just doesn't know how to act properly around other dogs. Does she NEED to get along with other dogs to live in your home? Is it NECESSARY that she get along well with the other dog that lives in the home also? If the answer to these 2 questions is yes, then you chose the wrong breed.
Dominance asserting is fine for dogs like GSDs and hounds and others were their origins aren't for dog fighting. A pit / pit type dog has origins which lie DEEP in dog fighting. With a pit when it goes, as said before, DA there's not much to do as a means of changing it... in fact I believe it gets worst with some dogs with age. If you're getting advice from people whom have never owned a pit / pit type before then you should take it with a grain of salt cause you can't apply what's dominance in other breeds to a pit [at least not safety for all dogs concerned in my mind].