Try to locate if you can where the smell is originating from. Check both of her ears, as yeast infections are common in the ears of canines and produce a foul smelling odor. Also check the vaginal area for discharge, any green or yellow discharge is a sign of infection and she should be seen by a vet asap. In some breeds, their skin oil glands emit a greasy substance that can cause an odor, very pungent smell. Check under her fur and look for small white dandruff looking white flakes, this and having an usually oily coat could mean her oil glands are over producing. Try medicated shampoo, sold in most pet stores, and you can try adding some sea kelp (powder you sprinkle on her food) to her diet. If she continues to emit a foul odor with no apparent cause I would suggest you see your local vet or clinic. For more information on herbal treatments, training or health tips, see my profile at liveperson.
My best guess is that she probably has a skin fungus and these do cause a strange smell.
Probably due to her diet. Dogs smell as we do. We just don't notice it on ourselves. All animals have a smell