Kennel cough is a virus (like the human cold) so unfortunately unless there is a secondary infection such as pneumonia there is not much the vet can do for you. Best thing is to make sure she continues to eat and drink (at least some), that she's still somewhat playful and give her some time. My puppy had it at 6 months old and he had it for about 4 weeks, but my girl who is 6 1/2 years only had it for about 2 days since she is older. It is a virus so it is contagious to other dogs. You will want to keep him away from other dogs until you know it's gone, but if he's living with a dog, I wouldn't worry about it too much especially if the dog is older. My girl, my foster, and my puppy all had it, foster and puppy both had it about a month, different symptoms but same thing. Snot, red eyes, coughing, lack of appetite because they were stuffed up and couldn't smell, sneezing, eye discharge, they were really pathetic there for a couple of weeks, but got over it and are now totally fine.
Basically what you'd do for a human child when they have a cold works for doggie. You can give some Vitamin C in the form of Ester C (found at the store) so it doesn't irritate the stomach, good premium food, a B-Complex Vitamin, and a dog multi vitamin to help boost the immune system but unfortunately unless there's a secondary infection that's about all you can do.
PS
My dogs never went to the vet for it, we just home treated, kept a close eye on them and all 3 were fine.