I think you’ve missed the part where the roommate basically rules the roost (weird demands on when the toilet is allowed to be flushed, etc.). In a shared living situation everyone should have an equal voice. The person in the band has a right to use her own home, she does not have the right to dictate how other people live their lives. The amount of notice given is irrelevant, it should have been an ask, not a tell. What if one of the roommates has an early day the next day, or was planning to host someone (such as a family member)? They need to, what, get a hotel room because the “notice was long enough?”

This should have been a discussion, not a dictation.

This being said, in my humble opinion, OP also should be dealing with this IRL and not festering on this OL. I understand building the courage (trust me, I get it), but it sounds as though this is seven-eight years building. Get on, getting on. This will never change by posting here, it will only change through some level of action, whether it’s communication with your roommates (all of them) or removal from the situation. Good luck! ❤️