Leanne Deacon, of Kibworth, England, is listed in critical condition after suffering cardiac arrest Tuesday minutes after exiting the attraction.
It's not yet known what caused her heart attack.
The ride she was on, the "Twilight Zone Tower of Terror," was reopened Wednesday. Tuesday night, Disney World allowed an official from Florida's state Bureau of Fair Rides and Exhibitions to monitor an inspection of the ride - which the park is not required to do - in an apparent effort to calm any public anxiety.
"I think they felt, in an abundance of caution, they wanted to help the public understand they're doing everything necessary to make sure the rides are safe," said Liz Compton, a spokeswoman for the Bureau of Fair Rides and Exhibitions.
Florida's major theme parks are not directly regulated by the state, and instead have their own inspectors.
The incident at The Tower of Terror - which plunges over 100 feet and is one of the most popular attractions at the Disney-MGM studios - is Disney World's second medical emergency involving a child in a month.
In a written statement Wednesday, Disney officials said engineers deemed the ride safe and reiterated concern for the girl and her family.
The incident occurred just one month after a young Pennsylvania boy died after riding Epcot's "Mission: Space."
Last month 4-year-old Daudi Bamuwamye died after riding Mission: Space. That ride is so intense that it has motion sickness bags and several riders have been treated for chest pain. An elderly, diabetic woman also died in February after riding the Magic Kingdom's "Pirates of the Caribbean," but the medical examiner said her death "was not unexpected."
Officials aren't releasing precise details of what happened, and Deacon and her family have declined interview requests. But incident reports show she felt nauseous and dizzy after exiting the ride.
Deacon at first thought she'd quickly recover, but park workers nearby noticed her and called an emergency crew. Authorities say before she arrived at the hospital, her condition deteriorated so rapidly that her heart stopped beating and she had to be resuscitated.
Orange County Sheriff's Office spokesman Jim Solomons says deputies who initially responded to the emergency scene were "satisfied that everything seemed to function okay on the ride" and that no other patrons suffered injuries.