Who would be at fault in a car wreck like this?

This wasn't my video but it's just like what happened in my case.

Basically, my fiancé was driving her silver Audi Q7 the way the camera car was driving. A red Honda Crosstour pulled out the way the van did and they collided.

So who would be at fault? My fiancé or the red Honda?

If the grey van was merging into that lane, they are required to yield to all other traffic. When the video starts, the van is already partially in the lane. The fault would be determined by how far back the car with the camera was when the van pulled into the lane. The video doesn't show that. There's nothing in the law that allows you to rear end a car just because they are in your lane, so depending on how long the van was there, the other car could be at fault. The video doesn't show the most important part, where the car with the camera was when the grey van began the lane switch.