>>107103309She has a student/work visa. She absolutely needs Niji for the work half.
Or some other company, if the work half of her visa is just for general employment and not specifically for work as an agency vtuber in a Japan-based vtuber agency. If she leaves Niji before the work half of her visa expires, she'll have 90 days to get a new job in order to not lose the visa; but Niji would absolutely enforce the 180-day non-compete clause to lock her out of other JP agencies, even if it would force her to leave Japan and stay out until she actually gets hired by another company.
When she first got to Japan, she was there on a student visa; but since her visa did not have a work endorsement, she couldn't legally do any sort of work related stuff while physically in Japan, even if it was the kind of work related stuff which could be done anywhere in the world with an internet connection (e.g. tweeting). She could not use any of her "Petra Gurin"-branded accounts to contact anyone at Niji for anything not directly related to her visa, until her student visa was changed into a student/work visa.
She'll probably change her student/work visa into a work only visa once she's done with school, whether she stays in Niji or gets a job with the degree she's trying to get. I doubt she has any plans to change her student/work visa back into a student only visa before changing it into a work only visa.