If every guy calls out a cockblocker once a month, it will cease to exist in a year or two. Girls only cockblock because there's no punishment. Since you can't slap her, use words. Don't use profanity or call her names—be mostly respectful so she can't write you off as an asshole. You're a good guy shocked by her rudeness. Use keywords: "respectful," "rude," "interrupt," "anti-social." I don't care if I get kicked out. I'm going to ruin her night and make her think twice about doing it again.