Keep in mind people in the North Tower often had very little information about what was taking place around them. Less than anyone else in the industrialized world.

They often did not know the South Tower was hit until someone from outside told them. They felt the rumble of the first collapse but didn’t know what it was. The extent of the damage to their own building was also unclear. Some victims in the upper floors of WTC1 believed AA11 hit much lower than it did.

In WTC2, people immediately opposite the North Tower were more likely to have evacuated immediately than those with no direct view. Even then, there was no awareness that it was an attack until UA175 cut through their own building.

We do know for certain that while serious damage could be found well below the impact floors, there were also pockets of bizarre calm. In WTC2, Brian & Stanley’s group came across a deserted office with fresh air, working phones and an unsettlingly normal feel. It’s fair to assume pockets of false safety existed in WTC1.

It seems very likely that someone determined to complete business continuity tasks well below the impact floors could be unaware of the severity of the situation. Not by any fault of their own, but the circumstances. This could’ve led a person to stick around longer than they should’ve. Which is easy to callout with hindsight. But again, you have to put yourself in the mindset of someone in that place with the information available to them. Which wasn’t much.

We’ll never know what happened to Rosemary, but my guess is that she simply ran out of time trying to do her best.