Hi all...and Welcome to Wednesday.
You might try picking up those adult incontinence pads and putting one under a towel or blanket that
I have a second waterproof mattress pad that I put on Samantha's bed....even though she wets through the sheet and onto the pad I'd rather throw those both in the wash than taking the cover off the dog bed.
My bed also has a waterproof mattress pad; I had bought one years ago that made the bed so "hot", but this one is much more expensive and you wouldn't know it was waterproof.
You're way ahead of me! Smart move :) Is she on DES? I had my aussie on it when she had bedwetting accidents when she got older and it helped her a lot.