Scarlie Poo

Well, Scarlet likes to take her diapers off at night!!! For the past month she has been taking her diaper off in the middle of the night, peeing the bed and moving to the other end to finish her sleep! I really don't know what to do. We are really lucky that her mattress pad is waterproof! :) I have to wash her sheets everyday. Does anyone have any suggestions? I am spent on this one.