Here is a time line of events of what we think happened (our reality on the left, alternate reality on the right):
However, if you listen to the audio, you can clearly hear that accident did take place, and Olivia has crossed over into an alternate reality but does not realize it.
Olivia continues in the alternate reality to her meeting with William Bell at the Mutsumi Hotel. When Bell is no show, Olivia enters the elevator to leave the hotel.
Originally we thought this is where she crossed over to the alternate universe, but if she is already there, maybe she is teleporting to the World Trade Center. A similar blue light was seen when David Robert Jones escaped from Wissenschaft Prison.
I think the elevator ride is where things get a little confusing. What do you think happened to Olivia?