In the beginning, Fil expected Marcus to lust over her. She expected him to want to do everything to get under her pants. It wasn't because she was being judgmental, but Marcus was a lowkey casanova. His past proved how little regard he had for love and marriage.
He valued friendship made of sand and connections more than the idea of settling down.
Not that Fil was convinced Marcus was not trying to take her to bed. However, after his confession, she noticed something else, aside from lust. His eyes brimmed differently as if he was looking at her because he was looking for something. His touches were also warm and caring; sincerity would often peek into his eyes and his complete aura simply gave off a different temperament than usual.
People could fake their smiles, how they react, and even their tears.