She should be worried, it's the 4th task. Scared?, perhaps trepidation would be the term I'd use instead. After all she's in a school full of people, in the bright morning light. There's not going to be a gangbang & besides L&P himself said that the tasks wouldn't be too extreme up to this point, (& probably well beyond, given past vanilla & blueballing form). This is a tale of corruption. Protagonists in these types of stories frequently look worried &/or miserable, as the corruption takes hold, whether coerced, semi-voluntarily or willingly. They're either wondering what comes next, or dismayed at the situation that their own acts & decisions have helped to create, or both.
Eroticism comes from the corruption itself & what it entails. (I assume breaking the taboo of incest provides the corruption & produces the eroticism for those who like it). Far from losing control over her personality Sophia should remain basically herself for quite some time to come on the blackmail route. Being forced into whatever she has to do means that she has not essentially changed. She may experience some thrill at the forbidden aspects & new experiences of it all but she has not taken a potion & become a different character.
Personally, as I've always said, I'd rather have a good woman coerced into outrageous behaviour, than see her relatively happy to do things like committing incest with her own son at some point, which for me does represent an actual genuine change of character, for the worse. IMO the misery, fear & sheer complete destruction of several lives turned inside out & put in a blender, that could result from this type of decision, far outweighs anything Aiden or Bennett could inflict.
Asking the Mafia for help would be a stupid thing to do but would be believable in the context of the story as it stands presently & though I know you're probably going to stick with the blackmail for now, I'm looking forward to all the Aiden-haters who wish to be rid of him making full use of the option, if it's what we think it is.