Does my guinea pig need hay?

We just bought a guinea pig, and we love her very much. My son lost his job and we cant even put gas in our vehicle, or buy his daughter diapers, so we can't afford hay for our piggy. We will be out of this tight spot in a couple of weeks, and I can buy her hay then, so I don't want to give my baby away, so is there any place I can get donations for hay, or can she have something else until then, I give her plenty of dandelion and carrots and grapes. Is that enough with her pellets until I get hay?