Smaller prey items that don't move as much such as a mouse fuzzy or a rat pup are sometimes better to try with. Also, like Homegrownscales said make sure your setup is correct and she has proper time to adjust. Also, if you still want to feed it a separate container place her in it and allow her to adjust to the new surroundings (half an hour at least) before dropping in the mouse, but it would definitely be less stressful to feed her in cage.