No one does. If there was a way to stop it, I'd tell you, but...all you can do is try to make it easier on yourself.

[ Which she probably shouldn't let the girl dwell on right now, so she rummages through the bag she brought with her and continues on somewhat briskly, in the hopes of taking Arietta's mind off of it a little with instructions. ]

Which, to start with, is to help you be able to move out of the bathroom. [ Arietta might do better to be follow Rapunzel's lead here unless she wants to be doing extra laundry, because Fenimore is enough of a luddite that she is producing a homemade cloth pad. ] This will catch the blood so you don't have to be worrying about it as often. Sort of like a bandage, but for your underwear.

[ Perhaps not the best metaphor, but she's never had to give this talk before. ]