I would suggest, short haired or long haired that you have her clipped back there and keep it clipped to make cleaning easier for you to do and to keep the smell down of it being in that fur. I would find something else to clean her with there, maybe a saline solution or perhaps baby wipes? Then I would put diaper rash stuff on there, she can't reach it to clean herself so she can't lick it off (after getting the vets approval).

It is time to put her on that dreaded "D" word just to make it easier and healthier on her. In the meantime, I would think you will need to clean her often until she is able to do that again for herself.