Who is KL in the nonfiction book, This Is Going to Hurt?

KL was Kay's favorite patient on the ward when he was a senior house officer. She was "five foot nothing of Polish sass" and her passing "knocked the stuffing" out of Kay (83). He decides to go to her funeral to which his consultant, Prof. Fletcher, tells him he cannot go as a result of maintaining a personal and professional line. However, Kay decides to go anyways.