unfortunatley you may find out the hard way that having a pet can be very costly, best thing to do is go to the vets and buy flea treatment, stronghold is best, it treats fleas and if there is a risk of Mange, this will also help, if this doesnt work then you will have to go to the vet for treatment, if you cannot keep her in the future, make sure she goes to a good home.
vet tech