In the novel The Mystery of the Blue Train, Annie is a girl living in St. Mary Mead, and working as a maid. Amelia Viner mentions her in a letter to Katherine Grey.
In Miss Viner's letter, she writes that she has been having trouble with maids, including Annie. According to Miss Viner, Annie's skirt doesn't cover her knees and she won't wear sensible woollen stockings. Annie, as well as the other maids, cannot bear "being spoken to" by Miss Viner.