Actually, I have seen a woman who apparently had a problem with her "monthly visitor" and was frantically trying to wash her shorts in the sink and dry them with the blow dryer....in her underwear. I actually felt kinda sorry for her. But at least she was in the ladies room, surrounded by somewhat sympathetic ladies. Point being, you never know what to expect in a ladies room. So seeing a topless woman is not a stretch....
Try the women's room closest to Kali rapids or splash mountain. There is pretty much always wet women in there trying to dry and often they are topless with their shirt under the dryer.
To the pp who said they used a companion bathroom to change a diaper there are changing tables in every wens and men's rest room and the baby care area so there is no reason to use a companion bathroom to simply change a diaper