In the novel The Secret of Chimneys, Elise is the lady's maid working for Virginia Revel. She is French and apt to get overly excited and launch into hysterics at the slightest thing out of the ordinary.
When Virginia returned home from some tennis, she found that Chilvers had obeyed a telegram purported to be from her ordering him to proceed to her cottage at Datchet and prepare it for a house party. Elise stayed behind to wait for Virginia, knowing that she would be needed to help her pack. When Virginia told her the telegram is a fake, Elise panicked and imagined that some robbers or thieves would be coming after them. Things got worse when Virigina discovers a dead boy in her study, her priority was how to prevent Elise from finding out (and hence becoming hysterical).
This is the first use of what would be a fairly common name that Christie would use for domestic staff, usually French.