The guy was Harvey Weinstein. Reports about Paz de la Huerta’s fall are often tied to the broader stories about her encounters with Weinstein, who she later accused of assaulting her in 2010.

Context

A 2017 Vanity Fair account says de la Huerta first met Weinstein years earlier and later described two nonconsensual encounters in 2010. CBS News also reported on her allegations against Weinstein that same year.

If you meant the viral clip

If you mean the video of her stumbling outside a venue, that specific clip does not clearly identify a companion in the snippet I found, but the person most commonly associated with her public fall-related stories is still Harvey Weinstein because of the surrounding reporting.

Why this comes up

People often mix together different Paz de la Huerta headlines: her red-carpet behavior, the Chateau Marmont clip, and the Weinstein allegations. That is why the “guy with her” question usually points to Weinstein rather than a confirmed bystander in the fall video.

TL;DR: it’s most likely Harvey Weinstein.