Dead rat --> maggots?

Take your rat to the vet! I'm sure there is something they can give your rat to get rid of the infestation. Another reason to take her to the vet is because you are not sure why your other rat died. There is no guarantee that the sick rat didn't give your current rat something, or if it is genetic. A few years back, I had gotten two dwarf hamsters, one died only after a month of having her. I brought in my other hamster and I was sure glad I did because she was sick too. It was something genetic, that had I not gotten checked out, my other hamster would have died also.