The only time where i can say that enrolling into a school is not a good idea. Her business needs MCs innovative ideas to work and expand, her enrolling to school might stagger their business' growth. Its an all girls school, hopefully it wont turn into yuri drama till she graduates
Uhh... did we just had a time skip?
Also I don't think going to school would be that bad. She'll get to network with influential people and that would potentially benefit her business in the long run.
To be fair if they are a "reclusive" school: no outside interaction, then
@Chucholain is most likely correct. Because she would be unable to provide information, updates or input for the business it would likely stagnate - at bare minimum even if "stagnation" is the lack of "advancement".
On the other hand, if she is still able to interact with her followers, especially if they can physically be with her (even if only by appointment), then
@karappo is likely to be correct. If she can continue running her business while at the school AND make influential friends and acquaintances then it will be worth while. And, honestly, what is she likely to learn (a new) there? Politics? Social grace? History? It isn't like she was completely uneducated before hand, and experienced an entire life before this, up to and possibly including college (the chapter didn't make clear whether "he" graduated or not...) so she can basically ignore all the basic classes utilizing previous knowledge, and use that time to work on her business.
But it all comes down to how restrictive the school ultimately is.