Cindy is interesting because we see an actual evolution in her sexual preferences. She starts off thinking she knows exactly what she wants, but Ian is able to open her up to the idea of anal over the course of the game. She seems to be starting to warm up to the idea of swallowing too. Cumming on her belly, telling her you like seeing her covered in cum, telling her you're going to cover her face in cum during the sexting, then later doing it in this most recent update earns positive relationship points with her. She at the very least seems to have a glazing thing developing, but the way EK describes Cindy looking at Ian's cum and goes out of the way to draw extra renders of Cindy scooping it up and looking at it... Just hints to me we'll see her doing some cum eating or swallowing at some point.
Edit: She also goes from a tit for tat on oral, to willingly giving a blowjob first without Ian initiating by eating her out.
None of the other girls really have any sort of sexual arc like this. Not even Holly. I don't think all the girls needed it, but it's interesting that Cindy was the one chosen to have this particular attribute.