You said she started off eating live rat pups or live mice & now refuses pre-killed mice? Why not try a p/k rat pup? It's possible she really prefers rats, but was more
stimulated to take either one only because they were live.
First, for her next meal, let a little more time go by between meals, so she is more motivated. (by offering every week, it adds stress anyway, to a finicky eater)
The way I'd personally train her to accept f/t is to first offer a live "appetizer" (small rat pup) & then immediately after, a f/t small* mouse while she is still in "feed mode".
*Just be sure that the 2 items together aren't too big of a meal. Some snakes will be pumped up enough to immediately accept item #2 after swallowing the first one, but some won't, & those you'll have to be patient, gentle & stealthy to "chain-feed" the f/t mouse into her still-open mouth JUST as she is swallowing the rat pup...& I do mean"nose to tail"...if you do it wrong, she'll ball up or spit out the mouse, but if you are subtle enough, the f/t mouse should get swallowed, & that should help acquaint her with the idea.
Better yet: just use 2 tiny rats, one live, one f/t...that's likely her preference & what you'll want to change her too anyway.