Here is a challenge!
I did French A'level in 1991 with the Joint Matriculation Board, which no longer exists. One of the set texts for literature was a sweet book about a young girl with a nickname, which I believe was the title of the book. Fairly sure it was a one word title
Possibly her parents may have split up, not sure. Don't know the author but it had a yellow cover! We also studied Les Mains Sales by Sartre and maybe Boule de Suif by Maupassant but this was more modern (at the time) and an easier read. Various internet searches have drawn a blank. Any ideas Mumsnet?