During the events of The Menu, there is a point in which Chef Slowik decides that Margot is on his side. As such, he complains that his trusted maître d’, Elsa, forgot to retrieve a barrel that he needs for dessert. He then asks Margot to retrieve the barrel.
En route to retrieve the barrel, Margot breaks in to his house. Elsa appears in the house and the two fight. During the fight, Elsa says "He did not tell me about the barrel. I did not forget the barrel. You will not replace me."
Considering what we find out about the events of the evening, we know that it would have been impossible to "replace" Elsa in any manner. We also know that Margot was not part of the Chef's overall plan as he repeatedly explains how Margot's presence ruins everything. It doesn't seem that he could have predicted she would find the radio and call for help.
What did Elsa mean by "You will not replace me"? Why did Chef Slowik lie about the barrel to both Margot and Elsa?