Some snakes switch to F/T right away, others it takes a little time.
Before we can answer about the switching part. How old is she? How much does she weigh? What food item is she on now (rat size)?
Then, when you are ready, we can tell you how to properly defrost and then heat and present the rodent so she thinks it's alive and is more likely to take it.
Just to be clear, it's your choice. If you think feeding live is better for you, that's fine. Just follow the safety guidelines and find proper homes/stores/etc. to take back the live rats.
It just sounds like F/T is much easier in your case, especially if your snake switches.