C.B.
Invest in a waterproof mattress pad. They aren't very expensive but worth every penny.
A friend told me to double sheet the bed so you don't have to try to change the sheets in the middle of the night. Starting at the mattress, put mattress pad, bottom sheet and top sheet on bed. Put waterproof mattress pad on top of first set of sheets then second bottom sheet and top sheet. That way, if she has an accident, you take off wet sheets and pad and have clean bed ready to go.