The best way to check for fleas is to brush her with a fine tooth comb. Tap the comb on a white paper towel to get whatever is on there off. Wet the stuff on the paper towel slightly. Then gently rub it. If there is red stuff, kind of like dry blood, then you've got fleas. What you are actually checking for is flea dirt (aka flea poop). Since fleas suck blood, it will be in their poop as well. The problem with flea shampoo is that the adults live on the animal but the eggs get into carpeting, upholstery, etc. So even if the shampoo works, she will still get reinfected from what's in the environment. And in case she has worms, I would wash your hands really well after petting her. And yes, people can get it.

If you take her to the Humane Society or Vet, they should scan her for a microchip. If she's registered they should be able to find her owners.

If she will allow you, give a quick once over. Make sure there is nothing obvious, no wounds, lumps and such. You can try to take a rectal temperature, rule out fever and possible infection. Not eating, drinking, urinating, or defecating is just not normal. Especially if she is a stray, she must be hungry. It could be that she's just scared or she's lethargic and depressed ("tired"). And she's most likely dehydrated as well. If you pull up on the skin behind her neck it should pull back immediately. If it stays tented then she's dehydrated. You should put her in a a quiet place and leave water and food. If she hasn't touched either overnight then I would be concerned. You might have better luck with canned than dry food.

Does anyone else find it disturbing that they design shotguns for CHILDREN ?!