I'm very much in favor of feeding f/t or fresh/killed (ie. dead prey) for safety (sooner or later, snakes get injured, sometimes badly, when rodents squirm & twist enough to get in a bite) but I've bred & raised many snakes, & I usually feed live to start off, just to make sure their instincts kick in properly. After several meals, they generalize better- they recognize the scent & they're hungry & used to eating in their new home, so they're more determined to eat. I would NOT try to switch to f/t prey yet- for best results, you want to feed your snake food that it recognizes for a few feedings- she's already stressed enough with a new home. Time to "settle in" (time for the snake to feel safe in new surroundings) is more important than you might think.
There is NO danger feeding live rodents (mice or rats) as long as their eyes are closed- they do not fight back at all. But, "fuzzy mice" as they're called, are too small to be a real meal- at least if you're only feeding one. (The equivalent to a hopper would be at least 4 or 5 fuzzies. Btw, I've also raised rodents for decades to supply all my snakes.) What was the breeder feeding her?
When it comes to feeding f/t, the trick with BPs is that the dead rodent MUST be warm enough- & rodents have a high metabolism.

So once you thaw* a frozen rodent in cool water (*check to make sure it's thawed by feeling the rodent mid-body by hand- it should all be soft, not frozen), then you want to soak them for about 5 minutes in very warm (not hot) water to warm them up, then blot off the water on a paper towel. They do cool off fast, so either offer immediately, or what many have the best results with is using a blow dryer- especially on the rodent's head to really heat them up right before offering. (No fancy hairstyling needed.

) Obviously, you only want to do this when you can see first that your snake is 'looking for prey'.
If you don't have feeding tongs, you need them- otherwise your nice warm hand has a bigger heat signature than the little mouse you're waving around...guess which one your BP will likely chomp on?

I prefer large (12") tweezers, but you can also use blunt-ended BBQ kitchen tongs to feed snakes too. Just don't get in their way, haha.
Now what I'd do with this snake to feed: if she's taking live fuzzy mice, I wouldn't try to feed her from the tongs. I also don't like to leave young rodents crawling around in a snake's home, because they sometimes get lost in the substrate, or the snake gets a mouthful of substrate instead of the rodent when they try to catch it.
A good trick with BPs (it helps them feel braver, like they have the "upper hand") is to put the live fuzzy(s) in a shallow flat bottomed bowl that's deep enough so they can't escape (about 2.5 - 3") and heavy enough so the snake leaning on the side won't tip the bowl. In this way, the snake can see, study, & strike the fuzzy in their own good time, in the dark of night (you don't have to stay up) & they feel safely out of reach of their prey too- snakes aren't always as brave or confident as you might think. They have to learn, just like all youngsters, & they get better quickly with practice.
BTW, that's a beautiful BP you've got there.
And- I almost forgot-

Snakes get much easier to figure out when you've kept them for a while- they're not like other pets, plus, they can have their own personality quirks too.