The video taken by the officer who was eventually hit shows that there was a medium- or large-sized dog in the passenger-side rear seat.
Speculating semi-wildly, it may be that Renee and Becca hoped to come to the scene, let Becca out to take video, have Renee block the street - both of which they did - have Renee eventually get out of the car with the dog, and provoke a fight using the dog. Only Becca knows what was intended, of course, but Renee's actions and the presence of the dog are suggestive.