Keeping my own personal database of LnC stories I've read does sometimes have it's advantage. The story I was thinking of is Tempus Junior and shame on me ( to Mellie) for not getting it sooner.
Are you sure its his daughter. There seems to me that there was a story where this girl from the future was studing him and got sucked into his beliefs or something. I vaguely remember the story as well. But not enough to really give a description. But there is definitely a story about Tempus with a daughter or a student being involved.