She more than likely IS in pain & showing it by not eating or drinking or moving.....I'm going with a possible Back injury....If so, she should NOT be going for walks......Karla
I agree with Linda. A few days without food and water could be fatal with such a small dog. And there are so many things it could be, it's impossible to give you any kind of advice on what to do, because I'd hate to make it worse. I know what it is like to have tight finances, but your dog really needs to be seen by a vet. Good luck!
If your dog is not drinking any water, and being so small, I would rush her to the vet. She won't last long without fluids. Also, she could be in pain and be hiding it, dogs are very good at doing that. Good Luck.