In the novel Postern of Fate, Elizabeth is the cleaning help employed by the Berefords before Beatrice. She was always coming to Tuppence and saying, "Oh madam, could I speak to you a minute? You see, I’ve got a problem." According to Tuppence, that meant she wanted to say something, but it was always defined as a problem.
There is some doubt whether Elizabeth was working at The Laurels or the previous place. Considering that the Berefords had just moved into the Laurels, would there have been a changeover from Elizabeth to Beatrice so soon? But during the conversation, Tuppence adds that "then Beatrice started coming on Thursdays and she must have caught it (the habit of saying she has a problem)". This suggests Beatrice and Elizabeth came into contact with each other and supports the idea that Elizabeth was working at the Laurels for a short while.