the teeth grinding is a guaranteed sign shes in a lot of pain - take her to the vets asap tonight for pain meds and metoclapromide or whatever its called that helps their tummies work! also I wouldnt change her food that quickly. and it may be that the car journey stressed her on the monday and caused her to deteriorate. I really have to stress that you need to get her to the vets tonight, a rabbit in pain will not eat and will quickly die!