It is Barty Crouch Jr., disguised as Alastor Moody, who states that Winky is in the top box, specifically the "box with the funny little elf". He does this to throw Harry off the scent of his true identity.
He wanted Harry to think that Winky was actually a Death Eater, which was a deliberate lie to protect his own identity.
There is no suggestion in the book that Winky ever claimed to be in the top box, or even that she knew what was happening. It's clear she was completely unaware of the extent of Barty Crouch Jr.'s manipulation and the dark magic at play.