M.P.
Is she still in a toddler bed? We have a plastic cover that fits over the entire mattress. That has been a huge help over the years for us. You still have to wash the sheets, but at least you don't have to completely strip the entire bed. You can just wipe off the plastic cover with a baby wipe and put another set of sheets on. I have also tried to stick the waterproof changing pads underneath them while they sleep, but my kids are WILD sleepers and that ends up not really helping that much. Good Luck!