It took us a long time to convince my husband to sit. He has mobility issues and it was just easier to wipe it up myself than risk him bending over to wash the floor and falling. My son was actually the one who told him he had to start sitting. I got to the point I put newspapers around on the floor.
The only problem with peeing in the tub is that after a while, the urine will erode the finish in the tub. She could have him do it with the water running. Same for the shower.