I understand your point and I was also contemplating that possibility, i.e. that the choice for continuing with the tasks or deciding to ask Morello's help may come very early when she is dressing up. Again she looks in the mirror and she asks herself why continuing and she remember Morello etc.
It is for sure a possibility, my only counter point is why then she still decides to dress like that if she is about to break the deal? Looking herself in the mirror she could think "ok enough is enough I'll go see Morello after school", at that point the deal is off and she can dress however she wants (i.e. normal clothes) because she will tell Aiden to f**k off as soon as she see him in school.
Some folks have complained that having Aiden threaten to beat up Sophia's son and another boy wasn't good enough blackmail to make Sophia acquiesque to his demands. I personally think that the threat was sufficient enough for a mother to agree to a few slightly degrading tasks such as teaching her class braless and flashing her panties for her students. Besides that, this is still a nice little story and we wouldn't want to immediately darken it up with Aiden sending Dylan's body parts home or burning down her home or something gruesome. Regardless of what we think, if we choose that path in the game, Sophia was willing to accept that deal.
But after Aiden's third task, Sophia was really pissed at Aiden. And what teacher wouldn't be angry that the class Bad Boy tricked her into exposing her body and played with her breast in public and pressed his "War God worthy" hardon against her flesh?
At some point in these progressive blackmail stories it often becomes necessary to increase the threat in order to keep escalating the payoffs. One theory I have is that Sophia is ready to tell Aiden to piss off now; but Aiden will be ready with some heavier blackmail material. What that might be, I don't know. Inflicting more pain on Dylan? Using something from the Third Task like blackmail photos or the students' paintings of her? I don't have a really good idea.
So, in this theory, Sophia may go to school with her bra on, ready to tell Aiden to piss off; and then Aiden hits her with more blackmail, Sophia gives in, and removes her bra (behind her desk crouching down?).