Just a few words of encouragement, Chelle. Raven is the only female dog I have ever owned, although I grew up with females.
Her history may be close to Rosie's, in that she was abused as well and we got her at about a year or so old, and that she had some "issues".
She spent about a year, challanging me for dominence. We had regular stare downs, growling and an occaisional snap. I think it was for alpha female status, and the only reason that Casey was not involved was because she was too young to be a threat. After about a year of constant reinforcement of my alpha status she did mellow. Ten years later we do occaisionally butt heads, but not as often or as violently, and she will back down much more quickly. I can't think of any better strategy than calling in a trainer/behaviorist to help you out, as you are already doing, I just wanted you to know that all is not bleak and this can be worked through.
Stella