Jean Webster 
Dear Enemy 

Dear Enemy is the sequel to Jean Webster’s novel Daddy-Long-Legs. First published in 1915, it was among the top ten best sellers in the US in 1916. The story is presented in a series of letters written by Sallie Mc Bride, Judy Abbott’s classmate and best friend in Daddy-Long-Legs. Among the recipients of the letters are Judy; Jervis Pendleton, Judy’s husband and the president of the orphanage where Sallie is filling in until a new superintendent can be installed; Gordon Hallock, a wealthy Congressman and Sallie’s later fiance; and the orphanage’s doctor, embittered Scotsman Robin ‘Sandy’ Mac Rae (to whom Sallie addresses her letters: "Dear Enemy"). Webster employs the epistolary structure to good effect; Sallie’s choices of what to recount to each of her correspondents reveal a lot about her relationships with them. (Wikipedia)