A similar situation happened to me recently.  An agenda and papers were sent to me for a meeting my boss attends on a monthly basis.  I noticed that the agenda did not have the same time as I had in the diary although the date and venue was correct.

A quick call to the PA who issued the papers was made, she apologised and said she would re-issue with correct time.  It turned out she had used the previous agenda - 'saved as' - and did not alter to a new time (usually the meetings are all at the same time but this particular one was different). 

She was grateful I noticed it and gave her a chance to put right.  Perhaps the PA you were dealing with Gee was a little embarrassed to be 'picked up' and reacted as she did - perhaps she was having a particularly difficult day and you caught her at a bad moment - could be any number of reasons.

Yes, she should have picked up that the time needed altering but at the end of the day,  not such a big deal.  I wouldn't have called her lazy for making this mistake but I expect that next time she is producing an agenda, this mistake will be in her mind and she will be careful not to make it again.

We all learn by our mistakes - there would be a definate problem if this error happened again and again but usually it only takes one mistake to ensure you don't do the same thing wrong again.

I don't think Gee you can say you were doing the work of the other PA or that she is not up to scratch in her job - surely we PAs should all rub along together doing our role and if you can help another PA (or anyone else in your office) that is a positive trait in the scheme of things.

We are all human and errors do occur.