It would have to be done quite subtly. What I mean by that is that if Sophia is being at all realistic / plausible / sensible / whatever word you choose, then she is going to be nervous about relying on the whole class to keep a secret.
So where it could work well is if the revelations come in stages, during this one task, so that Sophia thinks it is ok to admit to it. So for example if the picture that is shown is from early on when Sophia is fully clothed albeit still very erotically so, then it may feel to Sophia that she is ok to admit that she posed as an erotic model for an art class. Then Sophia might be willing to admit to that, as at that early point she has nt admitted anything too racy, and so she asks the class to keep it a secret.
But for this approach to work then would need L&P to very carefully write how the future developments are brought up e.g. showing her breast, wearing the skimpier outfit, posing with Ares. Aiden can't simply reach behind him to take out another picture, and then another, and then another etc....
Maybe if Aiden planted a question to be asked by one of her other students, who is not part of Aiden's friends, so Sophia is not too suspicious of it. So getting out maybe two paintings at most - the initial tame one and the later raciest one, Just thinking out loud.....