Continuity mistake: When the Suburban is T-boned, it is replaced with an older 92-94 Suburban with the front end of a newer 00-04 Suburban installed in place of the older front end. Older model 6 spoke wheels are installed instead of the 00-04 wheels shown in previous scenes. In one of the shots towards the end of the sequence, a completely different 96-99 suburban is shown rolling over with five spoke wheels, and the scene is mirrored.
Continuity mistake: Early on a pallet is leaning against a building with nothing next to it as two star members are backing up shooting at zombies. About eight seconds later you see an aluminum tube standing in front of that pallet. It then comes and goes. (00:15:00)
Character mistake: Jill states that a 5 kiloton nuclear weapon will sanitise the city, however, such a yield is far too small to destroy the city. (00:42:00)
Answer: The newspaper clippings we see in her apartment at the start refer to a 'mansion incident' - this in fact relates to the events of the first Resident Evil game, when Jill and other STARS members were trapped in a mansion overrun with the T-Virus. By the end of the game Jill knows exaclty what the T-Virus is and what its effects are.
Even though it mentions it in the newspaper clippings in the movie she wasn't even at the Mansion so therefore she wouldn't have known about the t-virus in the movie.
She was at the mansion prior to the events of Apocalypse, and one of the first ones to know about the virus before it hit Raccoon City.