How are you preparing the prey Item for her? Are you blow drying it to keep it warm to make it seem alive?
Also when she strikes it, do you go in there and jiggle the prey item a bit to mimic a struggle or not. Its important you do make the prey seem like its struggling a bit so the snake actually coils around it to secure the kill (if the snake isn't. Most snakes do coil though 99 percent of the time) and also if this isn't done the snake will never learn to coil stronger which could cause problems if one day you plan to switch to live preys, she wont kill them properly due to weak coil/choke.
But the behaviour is definitely weird to me, specially the part where she attempts to eat it (putting it in her mouth) then just gives up and lets go. May indicate that the prey Item could be too large or if not, maybe she's in a too stressful environment where she thinks there's imminent danger and doesn't have the time to swallow her fresh kill.