Falling out is typical, and at least it was from a toddler bed height and not the height of a regular bed! One thought: Be sure that the fall didn't scare her more than she's letting on--is she resisting going back to the bed, is she clingier or needier at bedtime than before the fall, does she end up coming into your room or calling you back, etc.? If those kinds of things start happening, the fall may have frightened her more than she's articulating in words. If not--great.
Does her toddler bed have any side rails? Both the ones we used, at our own home and her grandmother's, had built-in rails that ran just from the head of the bed down a short distance--not enough to keep a kid entirely in place if she wiggled down, but enough that if she rolled into them in the night, they'd remind her to roll back toward the center. If your child's bed doesn't have those, you might look for one that does. If you get side rails to add to the current bed, be sure they are a very good fit, or she could end up catching an arm between bed and rail.