I had just assumed it was a Barbara Metzger book...where the hero has ONE ARM and the young girl tells her friends she is going to marry him (she lives with her grandparents and her grandfather is a minister or vicar of some sort). A running joke is her insisting she is the grandaughter of a minister.
There is an early scene where she falls on the hero in the library, from the ladder and in the end the joke is she does indeed "win" her bet with her friends. Something to do with a chess set invovled? Read it years ago and would love to own it. I go to Amazon, no listing for it under Metzger! Was it Joan Smith? It was totally in the Metzger style, and it's sad as it's a book I would like to share with my daughter now.
Any help MOST welcome and if anyone knows where I can get a copy of the book I'd be glad to pay for it!