[Gmac]

Simple.

You don't discredit her, you humiliate her indirectly.

Not with logic, instead target her emotions. As bad as it sounds, you have to make her feel worthless.

I agree with tenderman. Make her self-conscious. Disarm.

Never debate.

I would have probably teased her for twisting my Buffet reference to fit her personal agenda, then looked away until she realized she had been cast out.