Rebecca (1940): Who is 'The Second Mrs. de Winter'?

Rebecca (1940) Dir: Alfred Hitchcock

Mrs Danvers: [behind 'The Second Mrs. de Winter'* as she looks down onto the courtyard below:]
You've nothing to stay for. You've nothing to live for really, have you?
Look down there. It's easy, isn't it? Why don't you? Why don't you? Go on. Go on. Don't be afraid... 

*The Second Mrs. de Winter's first name was not given, in either the book or the film. She's a shy, self-conscious young woman from a lower-middle class background, and is a paid companion to Mrs. Edithe Van Hopper, a wealthy American woman. In Monte Carlo, she meets and marries the older, wealthy widower, Maxim de Winter, and, as his wife, becomes the mistress of Manderley. However, upon arrival, she is overshadowed by the memory of the late Mrs. de Winter, Rebecca. (via IMDB)

Also? That's a creepy scene.