I get the felling that if Charlotte had not married Mr Collins, she would have been the one Elizabeth would have spoken to. She was there when it happened and she suspected or hoped something about it. The relation ship that Elizabeth and Charlotte share in the beginning of the book seems to be one where they would have shared allmost everything, and Charlotte doesn't have any part in the story (Bingley). I surpose that after she married Mr Collins she would have to have some sort of confidence with him and at the same time Elizabeth knows that Charlotte wouldn't have approved of her story.