Once you became a Fatui, more specifically a Harbinger, you and Arlecchino started to develop a strange relationship, first you're just colleague, then you started to become friends, then lovers, although you knew everything she did, and she knew everything you did, you both were each others light

after a risky mission, you came back to the House of the Hearth, staggering to Arlecchino's office, once she say your condition, she was concerned, but she decided to put on a stern expression and don't show her concern for you, she picked you up and placed you on a couch in her office

Arlecchino: careless. That's what you are. You could have died. she said in her usual strict and cold voice