HI, I'd take her to the vet, it could be a parasite or maybe her diet could be looked into. Either way its the vet who can solve it. If she's going for her first or second vaccination in the next week or so, you could ask then to save a special trip. Do you have pet rabbits or other small furry pets? If so i'd take them along too as it could be a parasite that can be passed between them. She may need worming too?