I just read in one of these darn books. I’ve totally lost track where I’ve read what. I think ”Remaking a 20th century legend”. I can’t recall the exact words but Simone told Sylvie the letters were all lost, but after her death, Sylvie found them neatly put away where she could not miss them when she was cleaning out her cupboards. They had already been edited by Simone so the authors insinuate she only wanted to make sure they were not published until after her death. It seems she knew Sylvie would publish them. Edited? So much for the truth.
To add to the story, these authors think she may have left them as proof that she came up with some of Sartres ideas and since she had always denied that, she didn’t want it revealed until after her death. This is sounding very familiar. I think I read something to this effect also. It's just so hard to remember what one read where. I have a real admiration for those working on a thesis or book on how they can keep all of their sources straight.