There's no one reason why. She's been busy with other things. She's been lazy. She lost her study materials when her baggage was lost by Alaska Airlines. Etcetera etcetera. I also think she secretly doesn't want to be promoted, because the job will take her away from dealing with passengers (something she loves) and put her in a position where she won't deal with passengers.
All of these reasons have contributed to her not being as ready as she should be for this assessment. But what peeved me was that, despite still having four hours and study materials available to her online, she felt it was "too late." My response: Chigaimasu. (Translation: Uh, no.)
Whether she doesn't want the promotion or she's just resigned herself to not getting it doesn't matter. She will be assessed today, and she will be evaluated based on that assessment. And she won't be as ready as she could have been.
Even if you are in a less than ideal position you should still be taking every opportunity to be as prepared as you can be given your circumstances. This goes for work assessments, school tests, international negotiations and dual meet two-mile races. "It's too late" is saying that preparation is an all or nothing thing. It isn't.
There is a bigger picture aspect to this as well. Will three hours of studying make a difference? Maybe not. Probably not. I have no idea. But it's never too late to start developing a good habit. It's never too late to say, "I'm going to get the most out of this that I can." It's never too late to begin developing an Optimal Training approach.
You may not see the effects today, but you will see them later. Champions know this. People who achieve excellence don't worry about the end result so much as how they approach the challenge. They focus on using their time and energy as well as they can, and they evaluate their performance on that criteria.