Hmmm. Let's start with the young lady. Orphaned, with a guardian who has plans for her she finds quite odious -- sell her off to the highest bidder or some such. She has to have some kind of plan for how she's going to live after she's ruined because otherwise she's just stupid. (Need to look in "Laws Concerning Women" to check some things on this.)

As for him -- a youthful indiscretion that got blown out of proportion or -- better still, he was actually trying to protect someone and it rebounded on him due to malicious gossip.

He'd probably be horrified at this girl trying to seduce him into ruining her.

This could work. Maybe once the wangst finishes eating my brain.