The fight in question, glimpsed in the film’s trailer, sees Rodriguez’s character Letty and Theron’s villainous Cipher waking up in a high-tech Frankenstein lap, each lying down on neighboring steel operating tables. They see one another, recognize each other, and immediately spring on one another, eager to do violence. The larger context of the scene will have to be discovered after the film is released.
According to the Vanity Fair article, there was no director on set for this scene. While capable second-unit directors may be present for action sequences or long, establishing shots, typically a principal director is going to be present for dialogue scenes and close-ups of actors. While this may seem atypical, Rodriguez chose to see it as an opportunity for punk violence. Why play with a net when you can freewheel? It seems that she and Theron were so well rehearsed, and both perfectly willing, that they simply filmed their fight scene themselves. Rodriguez even made a cute reference to the film that won Theron her Best Actress Academy Award. In her words:
“Can I just tell you — no pun intended, but Charlize is a monster. […] We shot our fight sequence with no director. Bro, like, hands down, drop mic, we nailed it. We were there, we don’t need [a director], let’s do this.”
That scene, it seems, kept production relatively on schedule while Leterrier was hired and brought up to speed. Rodriguez was careful to credit Theron for her willingness to film and fight as well, saying, “We kept that train running until Louie came in and took over. […] And [Charlize] is a consummate professional, sharp elbows, her work ethic is beyond.”