I'm going to second everyone's parmasean cheese, yogurt, canned dog food, and chicken broth as well as add canned baby food.
One senior dog I babysit sometimes goes off her food and I can usually get her to eat it by adding the baby food (different meat varieties) into her food. Sometimes I do have to hand feed her the whole meal as well.

I agree that you should try to make it as smelly as possible, and then try hand feeding it to her.

Good luck.