Sudden aggression in any dog warrants a complete physical. If nothing physical is discovered, then next step is (important to separate the dog from other dogs that trigger aggression in her) seek help from a behaviorist (Animal Behavior Society has a list). I never trifle with dogs that actually do damage to one another - it only gets worse without intervention. You may not be able to change your living situation, but you will probably have to change the way you manage the dogs. Get some professional advice.
Regional Director for Massachusetts, International Positive Dog Training Association
Director, SeniorCare Pawsitive Connections Program
AKC CGC Evaluator #3669
Therapy Dogs, Inc. Tester/Observer
Sioux, CGC, TDInc.
Maska, CGC, TDInc.
Sequoyah, CGC
Fergie, Retired Lap Dog, Age 19
Dancer, CGC, TDInc. (1989-2006) #1 Heart Dog
"If you talk to the animals they will talk with you and you will know each other. If you do not talk to them you will not know them and what you do not know, you will fear. What one fears, one destroys." - Chief Dan George
"The fidelity of a dog is a precious gift demanding no less binding moral responsibilities than the friendship of a human being. The bond with a true dog is as lasting as the ties of this earth can ever be." ~ Konrad Lorenz