Possible Clues:

• In there Lois expected another lady to appear
• Fictional Plaza Hotel resident
• Kay Thompson's Plaza girl
• The Parisian turned up on river and found the girl
• Plaza resident of story
• Precocious heroine of a 1955 book
• -- Jarvis McGraw, US author of children's books (1915-2000)
• Literary girl in Paris and Moscow
• Kay Thompson title girl
• 1968 single by Barry Ryan, written by his twin brother Paul