German shepherd female dog aggression

Question
I have a 3 1/2 year old German shepherd female named Raven. I acquired her when she was about 10 months old and introduced her to my other two dogs, an older male shepherd mix and a small female Australian shepherd mix. Raven is fairly high-strung, but she adjusted pretty well, although it took at least six months for me to feel that she really trusted and loved me. I don't know much about her first 10 months, but I don't think she was socialized to other animals as well as she could have been. I have worked sporadically on obedience training, and she is very good at sit and stay, fairly consistent at down and come. She and the other three dogs are confined in separate outdoor runs when we can't be outside with them. We don't have a fenced yard, but they are out for exercise every day, more when the weather is good. Raven is very friendly with people and has never shown aggression toward any person, regardless of age or how they behave toward her. She seems to have an alpha dog personality, though, and she has been exhibiting increasing aggression toward my other female dog, even to the point of attacking her with no provocation that I can see. Xena, the Australian shepherd mix, is never agressive and she avoids Raven as much as she can, but she isn't submissive either. Raven needs a lot of exercise, and I spend more time with her than the other two dogs. I try to watch her carefully when all three dogs are loose together, and although she often runs at Xena aggressively, I can control her with a sharp NO or other command, if I stop her before anything gets started. Several times during the last 18 months Raven has attacked Xena and appeared to be trying to kill her. I have been able to get Raven off her within a minute or two, but it's terrifying for me and of course for Xena. In the most recent attack, Xena was injured, and I'm afraid that this behavior is only going to escalate. Raven becomes ferocious and frenzied--she doesn't respond to anything I say or scream. My husband is never there when this happens. She seems to recognize his authority more than mine, although she doesn't ever challenge me in an aggressive way. How can I stop this behavior without having to keep the dogs completely separated?  I use a choke collar and sometimes a gentle leader on Raven, but I'm considering using a muzzle when she's out with the other dogs. She is intelligent and loving, and I'm very upset about this problem--I want us all to be able to live in peace together. I hope you can help me.

Answer
You don't say if they have been spayed.  If not, spaying them both should help.  It is no cure all.  You must work with her and get her to recognize your authority just as she does your husband.  The key to most behavior problems is approaching things using the dog's natural instincts. Dogs see all the people and dogs in the household as a pack with each having their own rank in the pack and a top dog. Life is much easier if the 2 legged pack members outrank the 4 legged ones. You can learn to play the role of top dog by reading some books or going to a good obedience class. A good obedience class or book is about you being top dog, not about rewarding standard commands with a treat. A class would be good, both disciplining you to keep up the lessons and avoiding aggression towards other dogs in the class.  The instructor should provide some hands on help in that area.  

Otherwise, you may need to have a private trainier.