The Apothecary Diaries 1x06 Full Reaction

Just to clarify the situation between Lady Lishu and her servants: In the beginning of the episode, her servants were annoyed about her being such a picky eater. So out of spite, because they had to accommodate her special requests, her lady-in-waiting swapped Lishu's food with that of Lady Gyokuyou, not knowing about the poison or her food intolerance.