So the friend is embarrassing the ex?
She could spill things on his clothes. A bit of a classic, yes, but it bears mentioning. People generally want to go home if they’ve been doused in beef broth. She could also spill something nasty af of him like old food or sour milk. (emetophobia warning for this next sentence) Bonus if she can retch on demand and puke on his shoes
She could drunkenly tell tales of how he peed himself at a previous party, even if it’s not true, or other rude and embarrassing stories. Or ask him pointless and invasive personal questions to make him uncomfortable
hope this is okay! Sorry it’s so short!