You: repeatedly keep looking at your watch Her: "Why do you keep looking at your watch? Do you need to leave?" You: "Oh, no. Not at all. My watch communicates with me telepathically and I was just listening to it." Her: "Oh yeah? And what's it saying?" You: "It says you're not wearing any panties." Her: "Ha! Well it's wrong." You: tapping watch "Yeah, it's always been running a little fast."
Yes, that entire thing is the pickup line. Girls get jelaous when they see you're interested in someone else other than them in the room. They also drop their guard when it is just a "friendly chatter" or simulation.
Outcome? she may start playing along or say "Fuck you" and go away. Either way it's a play big or go home move.