Big girl bed!

Any suggestions on how to keep your LO in their toddler bed? She loves it, gets in and goes to sleep and never gets out on her own BUT she wakes up close to 4-5X a night because she falls out of bed. I’ve got one side up against a wall and I’ve tried rolled up towels under the bed sheet on the other side. This is the bed. I don’t want to switch her back to a crib because she loves and is doing so well with her big girl bed but I want to make sure she’s getting enough rest as well!