It's not unusual for adult females to go of feed for a long amount of time when changing environment, the key here is patience, optimal husbandry and feeding the same prey than what was previously offered.
Because she is big enough for a large rat does not mean she needs to or should get a large rat, if you want to have an animal feeding with consistency feed smaller preys this will also allow you to feed live without issues.
The largest I feed are 125/150 grams rats and those are only meant for females 3000 grams and over.
The key to live feeding
Scenting the room
Making sure the feeder is well hydrated and well fed (offer food and water if you purchase your feeders from a store)
Feeding a appropriately sized prey
No stunning,not only is it inhumane for the prey but in the event the feeder wakes from it's daze it could make it far more dangerous for your snake.
Monitor feeding
Remove prey within 15 to 20 min if uneaten.
I feed 250 live prey a months to my breeders and never had an issue, many do the same without issues either.