I am unsure why an old man would have felt it appropriate to discuss his sex life with an 11-17-year-old to whom he stood in loco parentis.
Maybe something might have come up at the funeral? Maybe?
But the sex lives of most of the teachers aren't brought up either - the books are from the POV of a child/teenager, in a culture with a lot of Victorian overtones. I suspect most of them simply did not consider it an appropriate area of discussion with the kids.
Re: Why would she have to write a romance at all?
Maybe something might have come up at the funeral? Maybe?
But the sex lives of most of the teachers aren't brought up either - the books are from the POV of a child/teenager, in a culture with a lot of Victorian overtones. I suspect most of them simply did not consider it an appropriate area of discussion with the kids.