I inadvertently left my cat home for 4 days without food and water. She seems okay, but should I take her to the vet?
I think you need to take her into the vet for a checkup. That's a long time without knowing the state of her nourishment and hydration. I would advise that for anybody that hasn't had proper nutrition for more than 24 hours.
Why? The vet can check to make sure her weight loss isn't too bad and supply specialty food for weight gain if needed. They can also check her hydration level and do some subcutaneous fluids to help bring it back up. A good look-see is a a good idea.
If there is a chance that this can happen again, I strongly recommend that you supply a ready supply of dry food and water. Most cats won't eat it all, they'll eat when hungry. This removes the risk if you keep things topped up regularly.