What was the Aircraft commander doing while all this went on. Based on the footage she had plenty of time to do alot of things.
One report said the two aircrafts’ closing speed was about 175 mph, or 250 feet per second. I’d guess a qualified and fully aware pilot could deal with making an successful avoidance maneuver in 5 seconds, starting at 1/4 mile apart. (I have no experience with such things, so definitely a guess). A pilot in training maybe not. Was her “plenty of time” lost in indecision / disbelief of what she was seeing?
One way or another, she either didn’t see it, didn’t see it until too late, thought she would fit under it, or didn’t care.