If Arisa's this keen on upholding rules, even those she considers absurd, she's going to have a rough time going anywhere outside. Have fun seeing a lot of restroom facilities that are boys-only, whilst the few public women's restrooms you find will have a giant line and will be right next to a nearly empty men's room. You're the maker of your own misery here.
Anywho, I'm guessing this is some kind of coping mechanism as a result of some past events we haven't seen yet as this chapter goes out of its way to show how Arisa's also suffering under the same ruleset she wishes to uphold.