other dogs

Question
my GSD is the soppiest thing around. I have 4 kids and she adores them. I sometimes think that she thinks she is a human. The problem is in the last 6 mths she has become extremely aggressive towards other dogs. She was not like that before and actually used to be scared of other dogs. she is not like it when in a big open space, she actually doesn't pay any attention to dogs then but if in a small space and a dog comes in the room she goes nuts. I thought maybe she is just getting a bit grumpy in her old age (7yrs) but just wanted to see if there was something I should be doing. Last week we were in the bar at our rugby club and a dog came in. She went loopy, but i told her no and then everytime she started to growl I looked her in the eyes and said no. After about 10/15 mins of this she laid down and went to sleep even though the dogs were still there. I think this all started when a dog took a bit of food out of my little boys hand, she went berserk and since then this is what happens. sorry such a long message. Do you think she is just being protective? thankyou for your time.

Answer
Seven is too old to be maturing, and too young to be old and grumpy.  Likely the food stealing is the problem.  It would also be good to have the vet check her.  See if the vet can suggest a good obedience class.  

I think the problem is that she thinks she is in charge and it is her responsibility to make sure no other dog steals the child's food.  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  That site has some more material on dogs and children you need to read.  I really think you need to take her to a class. Discuss the problem with the instructor before hand.  She can only learn to behave well around other dogs, around other dogs.  

The more details you give, the better answer I can give.