Er, I didn't get the bonus points to magical theory.
"Sigh...Miss Marcy, if you don't come out of that tank, you won't Forget that eldritch magic. Bathing in that water won't be that good for your skin. Marcy, I can promise you that I will avoid teaching you magics without your consent. As for the others, I am sure we mages can reach an agreement about what not to involve you with.
Archeux looked through his belongings for a gavel, and, failing that, decided that knocking on a table would do well enough. He called out, on each of the floors, that he would be holding an impromptu guild meeting on the fourth flood to address some rules for preserving the princess's mind, body, soul, sanity, existence, and, most of all, interest in learning magic.
Continue her education on general magic, from within the tank if necessary. She won't be able to do basic, general spells from in the tank, so the next classes will have more of a focus on the two of them figuring out what branches of magic she is innately interested and attuned to.
Archeux knocks on the table in a firm, yet awkward manner. "I have called here a meeting amongst ourselves to impose some rules upon ourselves for the preservation of the princess. I have only _ rules in mind, but these are but an outline on what we could agree upon, if anything. Firstly, whatever we try to teach or do with her, we should have consent in the first place. If she changes her mind afterward, though, we can still proceed with our lesson. Second, we are able to deny the princess a lesson if more people oppose the lesson than support it, but she can veto this if the opposition is less than double the support. We may not have any Oathmaking mages here to enforce this, but there should be enough trust among us for the time being. Now, who is in favor of these rules, who would like to suggest alterations, and who has not attended the meeting? "