If 348 died at the WTC then there should have been a much greater number than 343 present and there should have been at least 1 female there if not more. Assuming those who entered the building had a 100% chance of death, there is a good chance that there were females present and none of them entered the buildings.
Agreed there would have been more than 343 present, haven't seen any figures on how many were at risk. I had assumed some of those who entered the building made it out safely - perhaps some who had just helped someone out, some regaining their strength, some who didn't go in after the orders came to evacuate.
The article doesn't indicate there were any women firefighters in the building. Given the stats, it's possible there weren't any.