The sexual favors were NOT part of the deal, that was ALL Aiden!!! The deal was to make Sophia dress sexy and that was it or he would "beat up Dylan" and just once. The sexual favors, the 12 tasks, the phone number exchange...all that, it's Aiden all alone not part of Dylan's agreement.
If we're talking about real-life...then I will have to surmise that...then the Love was already weak among them or among any relatives.
A real-life mother's love is far stronger than you would see on a VN and if you think you can't come back from that...then the love was already weak, minimum, interested based on standards instead of being unconditional and forgiving. Maybe you have a different set of standards, maybe you have a different set of cultural background or family behavioral priorities, but from where I come from Family is always first, the family is always together, and family is always forgiven and loved.
Yeah, his mistake was trusting Aiden and that Asshole took advantage and changed everything, but even after leaving, Sophia understood that it was well-intentioned, EVEN after a few moments of leaving the school and know the truth she was already trying to understand her son. She loves him, she'll forgive him.
Unless of course your mind is made up, set, and unchangeable and if the choice comes up, you will pick to not forgive Dylan or even yet, sentenced him already before defense nor solution and drop the path altogether. It's all up to your own mind, but I will opt to make it work for them and continue the path.