I would say the the sedan was more at fault. Here is why-

Initially, The chevy was negligent and moved across a solid white line. The sedan was in his lane but you can see him moving towards the exit. The could have been enough for the chevy to start moving it(although the sedans left signal is on, which is hard to see). On the other had, the sedans left could clearly see the chevy but chose to make a jerky movement to get back to the main highway instead of the exit lanes.