My dog throws up everything she eats. I don't know what is wrong with her and I can't afford a vet.

Is she getting enough water?
Maybe she needs a different brand dog food?
Try giving her a can of pumpkin and some pedilyte even if it doesn't stop her from vomiting it should balance the electrolytes she has to be losing from all the vomiting.

Save up and get her to a vet as soon as you can though