simple: say "sorry, im just not into you" if they hit you with a "who then" you rely with "wouldnt i like to know" the proceed to remove yourself from the conversation.
IM PRETTY SURE A GIRL IN MY CLASS HAS A CRUSH ON ME, AND I'M PRAYING THAT SHE DOESN'T SAY ANYTHING BECAUSE THEN I WOULD HAVE TO OUT MYSELF AND THAT'S A BIG NO NO😭