In this scene from "Summer, Kind of Wonderful," Nate and Serena are just acting as though they are together ... so peeps will leave her alone about Dan and no one will question Nate's scandalous affair.
Serena: Blair will never forgive you for what you did to her. Chuck: Who told you that little piece of advice, your boyfriend Nate? Serena: Nate didn't say anything ... Chuck: Good. I don't think it's wise taking relationship advice from someone in a FAKE relationship. Call me crazy. (pause) Enjoy another night alone with your thoughts. Serena: Good luck on your suicide mission!