Please have your piggy seen by a vet.
If she is not eating hay (ie. three quarters of the daily foot intake, not drinking and only nibbling on a little lettuce), then she must be in great pain and have likely internal injuries from the fall. A veg only diet can casue soft poos because it is the hay in the diet that is responsible for the bulk and the healthy consistency.
After her experience, and in view of the pain she must be in, I would would also fight being handled.
You need to step in with feeding support asap; this link here contains all the necessary information; including what you can do with what you have at home or easily available because guinea pigs cannot afford to fast:
All About Syringe Feeding and Medicating Guinea Pigs with Videos and Pictures
Here is our emergency and crisis care link with all the necessary support care information, including how soon and when to see a vet (loss of appetite and a big fall definitely count as such) plus a chapter on how to spot when your piggy is dying:
Emergency, Crisis and Bridging Care until a Vet Appointment
You can show the links to your parents or a vet if needed. The Emergency Care link also contains links to safe and unsafe medication if you are seeing a vet not familiar with guinea pigs.