our dogs are suddenly fighting

Question
We have a new puppy 8 months old and also a 10 year old both females.  The puppy is a collie and golden retriever mix and the older dog maggie is a german shepard and rotweiler mix.   Whom I have never seen growl or show her teeth until today. When we brought home the new puppy both dogs took to each other and they got along beautifully up until recently.  They are fighting rather violently where I need to seperate them and it is very scary!  The last time it happended my daughter witnessed the onset and she said it is our older dog Maggie who started it.  We have a feeling she is suddenly jealous and is acting out.  Could this be the case and if so what is your best advise on how to handle this.  During the day when we are away from the house I'm now afraid to leave them alone together.

Answer
This is a tough question, and not one I have experience in.  Perhaps I should have passed it on to the question pool and see if somebody else could do better.  Two females is the combination most likely to have problems.  If both dogs have a high dominance drive, they may never get along.  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. Start at http://www.dogsbestfriend.com/  For more on being top dog, see http://www.dogbreedinfo.com./topdogrules.htm

Spaying both dogs may help.  If the 8 month old isn't spayed, she could be coming into season accounting for the problem cropping up now.  It also could be she is causing the problem.  There are subtle ways a dog can challenge another that your daughter may have missed, body language, eye contact, head position, etc.  

I can't promise better leadership and spaying will help, and certainly not right away.  If the younger is coming into season, the vet likely will want to wait until it is over. There are cases where a good professional trainer or dog behaviorist can help if you found one.