Here are some protips on how to derail:

• mention circumcision
• bring attention to her emotional state. Mention her period. If she denies it, Use lots of ableist slurs to make sure you think she's unstable before mentioning therapy as an option. You know this because your experience on reddit makes you a licensed know it all.
• focus on her cloths or diet and make the discussion about how the entire topic is now tainted because of her judgment on things that have nothing to do with the topic.
• get distracted by trend words that she may have used in the discussion. Seque into a giant butthurt complaint session about how Millennials are ruining everything.
• mention circumcision
• no perfect derail happens without a guilt trip. Lay on some heavy guilt that you don't get any attention for not catcalling. What are you supposed to do to get some love? Women like her are making it impossible, ruining the world and is bringing about the extinction of the human race. There is no limit on hyperbole you can use when guilt tripping.
• mention circumcision
• mention women in other countries have it worse. Guilt trip her into gratitude.
• use a personal outlier anecdote to PROVE HER WRONG. Your dad catcalled your mom and that's how they met. Had he not, you wouldn't exist.
• simultaneously forbid her to use any anecdotal examples as evidence. Make it about statistics and science to PROVE HER WRONG.
• evoke Godwin's law