I have a feeling that there was an emotional component for this woman. She may not have been ready to return on Monday.
May I interject, in a been-there-done-that format, the departures of large units don't always get off without a hitch. There are speeches and formations and hugs and kisses and gathering of gear and loading up and putting out the fires that always seem to crop up at the last minute and paperwork and a little bit of chaos thrown in, to boot.
So if the Indiana troops were scheduled to be off by 3:00 and didn't actually get away until 8:30 (again, been there, done that), expecting this lady, emotionally drained and under extreme duress, to drive 300+ miles and then get up bright-eyed and bushy-tailed for her receptionist job the next morning may not have been feasible. Thus her comment that she told them she would try to be there on the 17th, but if she couldn't, she would definitely be there on the 18th.
Without knowing indepth details at this point, I'd say a little compassion and leeway would be in order.