Sara, Marion Crawford was the governess hired by Elizabeth Duchess of York to look after and teach Princesses Elizabeth and Margaret in the early 1930s, and she stayed until Princess Elizabeth was married, so she was with the family during the abdication, the second world war, and Princess Elizabeth's courtship with Prince Philip. She was an employee, not a family friend. She finally left royal service after her own marriage, which she'd put off several times because Queen Elizabeth never thought it was convenient to let her leave earlier; she was somewhere around 40 when she finally got married.
It seems to have been her husband who persuaded her to write this book because she was being offered quite a lot of money to do so; some people had already written about the royal family, but their articles and books were always either invited by the royal family or at least pretty heavily controlled so that the message going out was the one the royal family wanted to project. In contrast, Marion Crawford's book was her own work with no input from the royal family. She'd previously asked permission from Queen Elizabeth (the Queen Mum, not the present sovereign) to contribute some articles to a magazine and been refused, so Queen Elizabeth was very annoyed that she went ahead with this book.
And, just as with the Duke and Duchess of Windsor, when Queen Elizabeth took against someone, she never, ever let it drop. Marion Crawford was made to leave her grace and favour residence, and the royal family behaved as though she didn't exist, except that acts of personal betrayal toward the family were known from then on as "doing a Crawfie."
Interestingly, it seems as though Queen Elizabeth was prepared to let Miss Crawford contribute to articles about the royal family in American magazines as long as she didn't put her name to them, according to this article:
http://www.guardian.co.uk/monarchy/s...336142,00.html