You know, Yuu was not in as bad a situation as she thought, even outside of the whole love bias. Just emphasize how killing the person who dissented with you would be very sloppy, and how that contrasts with current actions. It'd be risky and rely on your acting skills being better than your (in this hypothetical case not girl-) friend's understandings of you, but it could throw a lot of confusion onto Sayaka's accusation.