It's your decision, but I agree it's important that a young snake keeps eating. If you think she may have been fed live, then I'd try that- but just make sure what KIND of live (rat or mouse) as they smell, taste & act different, & of course, must be the right size. Mice- most BPs are big enough to take hoppers, but they can be quite active & scare the snake. Fuzzies are really too small- not enough to eat, but can sometimes make a good "appetizer" (some snakes that only recognize "live" may go on to eat a f/t one if offered immediately- in fact, that's one way to "teach" them).
*******And I'm assuming you're sure all the other bases are covered? (as to all the issues we asked about?) Specifically the feeding techniques I mentioned in post #4?
I don't know what the guy you spoke with meant either: maybe by "bigger ones" he meant the larger, well started hatchlings, but why they'd switch from f/t to live is beyond me?
Snakes are mostly deaf, but they do feel vibrations (& bass notes). If her home was in a living room, for example, where you played loud music/tv, & people walked by frequently, that would tend to make a snake nervous. It doesn't sound like that's any sort of issue.
I hope you're patient, some snakes can be challenging to get started.