Obviously I don't have evidence for this (I don't have the design docs or anything), but there are two potential places (aside from other girls' content) where more Jenny story could show up even if her main path is 'done' - the dating system and prom night. Given the diary as well as the interactions between Jenny and MC, it seems pretty clear that Jenny eventually falls for MC, is willing to 'girlfriend' him, and that the MC generally wants to go out with her as real boyfriend and girlfriend. She even seems a little surprised that he wants to stay inside for their date. Given that she's already been willing to go to the movies with him (and bang him, obviously), I don't see any reason they can't go on more dates and that that couldn't advance their story more. I think that's where we could see them transition from paid girlfriend and boyfriend to real girlfriend and boyfriend. No guarantees, but I think it would fit.
In essence, I feel like the 'dating' system is probably a post-romance thing to do with ladies. Otherwise, why make it a separate system at all?