You recently acquired this snake, but what did the previous owner feed her? You need to do the same for now, while she is settling in with you (change gradually
to f/t later...please!!!) When you offered f/t, how did you do it? Using tongs? Make it appear to be alive? Heat it up??? Your method may need improvement.
Often it's US that need to learn, not the snake. Too much or too little motion can turn off a snake, & snakes aren't all the same as to what they like.
FYI- Live rats can kill a snake...what size/age is the rat you tried to feed? Sizing DOWN might work? Or better yet, if she had always been fed live rats (?), try
offering her a live rat pup as an "appetizer". (rats or mice with eyes closed do NOT bite back...all others, with eyes open, do bite and pose a risk to your snake)
Some (not all) snakes will be pumped up after killing & consuming a rat pup to go on and take a larger pre-killed one (much safer & often your snake may learn
to just accept either fresh p/k or f/t this way).
I know (first hand) how frustrating some snakes (esp. BPs) can be to feed...you have to keep trying & not give up. Feeding live rats is NOT the long-term answer-
sooner or later your snake will be injured badly or even killed by an infection from a rat-bite. It's entirely possible she has already HAD a bad experience with a rat-
and is deliberately "missing" her mark, or hesitating & thus failing to connect.