If the dog she was living with at your parent's house behaves this way then she could definatly have picked it up from him. Also, all the moving around and different living situations (I totaly understand that it had to be this way given the deployment of your husband) has most likely made her feel insecure which can definatly cause agression towards other dogs among other behavior issues.
Instead of writing a very long plan for you here, I'll recommend you to Cesar Millan's books.
