Unless Harper had snuck in some tech in her teeth or something that recorded Punchline's confession through her gloating, to be used later to expose her. Which she could have done, but again the comic portrays it like Harper's way in over her head instead of that she was baiting her into a confession. Not to mention they seemed to have forgotten the master tactician part by making her feel the need to go in there to infiltrate and talk to Punchline without any kind of tech or plan. Punchline made her look like a rookie, and I doubt that they'd go back on that as that's how they seem to think that's how to make Punchline work, at the expense of other characters.