In my experience the feeding is the first to go when they get sick. Now that's not to say they wont eat, it just means of the few RI's I've had to treat the animals don't eat. Is she whistling or popping when she breaths. Snakes mouths aren't dry they do have a supply of saliva that helps with getting food down the hatch..

The best thing to do is if you suspect that the animal may have an RI then a Vet trip is in order. Only a Vet can prescribe the needed meds and make sure to get what the animal needs