Evidently I haven't made myself clear: mine is not a fantasy of seeing Sophia as Aiden's whore, but rather a conjecture as to why she should dress like that for a simple meeting at his headquarters.
In my opinion, if anyone came out of the fourth task really badly, it was Andre:
- he failed to grope Sophia's breasts, when all of Aiden's task (especially if he had succeeded the day before) seemed directed for him to be the lucky student to enjoy such a show,
- he got a slap from his teacher, who moreover ridiculed him in front of his loser classmates (at least that's how he and Aiden think of them),
- and, to top it off (if Sophia intervened to prevent it), he also failed to collect the winnings from his bet with Aiden (his girlfriend Jennifer)
Therefore, as I have already told you, if Aiden wants to prevent Andre from doing some other bullshit (like the one he just did in the classroom), he has to give him some small satisfaction. Now, since Aiden has already proven that, for Andre (as probably for all the other gang members), Sophia "can be looked but not touched", my guess is (as a small consolation for his friend's bad day) he will force her to show her breasts to Andre.
How to accomplish this, according to Aiden's twisted logic? By placing Sophia in a situation where she has no choice but to accept his proposal. Hence my hypothesis of the terribly awkward task of the "fake" prostitute as an alternative option. This, to me, would explain why Aiden would want Sophia to show up dressed as a streetwalker on their meeting.