Dog won't eat or drink?

I am boarding a dog whom has yet to eat or drink anything since she has been at my house. It is my first time watching this dog (small-breed, middle age) and I know that some dogs need some time to adjust to their new surroundings. It has been around 32 hrs since she came here, and only drank a small amount of water upon her arrival. Other than that, she seems repulsed by her food and water. I've cleaned out her bowls, even tried other bowls, but she does not want to eat or drink. She seems happy and healthy, otherwise! I've contacted the owner, and she's says not to worry about it. I am more worried about her lack of drinking. Any other sitters experience this refusal of food/water with new dogs? How long did it take for the dog to eat/drink again, what did you do to help?