Revealing mistake: In the London scene, when the main characters prepare for the Centipede attack (the scene with the football players) there is a grey Land Rover which has a fake UK number plate on it. Plus since the film was filmed in Canada, the car also has left hand drive windscreen wipers.
Revealing mistake: When Brenner and Cooper are at a bar, they are watching a news report of Cooper at a school reading to a group of children. There are a couple of times in the report that show a shot of the children, but whenever the shot is on Cooper, there are no cameras in sight that would be used to film the shots of the children, revealing that the shots of Cooper and the shots of the children were filmed separately.
Answer: She was a pixel but turned into an ordinary person. Probably to make the fight look epic.