Allow me to try and clarify. *Potential Spoiler Alert*
In Broken Sword 2 : The Smoking Mirror, whilst on Ketch's Landing, Stobbart meets Ketch's descendants Frost & Mina. He discovers that they have a niece called Emily. George finds out that Emily & Rio like to play with each other, & the Ketch sisters loathe Rio, so George tells them that he has seen Emily & Rio playing together. They are just as baffled as Rio is when you explain to him your diversion.
Whilst in the museum, you open a chest and out pops Emily. If you talk to Rio after speaking to Emily, he still seems confused. At one point when you're with Emily, rather than turning around 180 degrees, she "fades" around. Then when you reach Zombie Island and talk to Rio, he tells you the story of the last time he played hide-and-seek with her, as she his in a chest that can only be opened from the outside.
The story heavily implies that she was trapped and died from either starvation, suffocation, or both. Add that to the "ethereal" animation I referred to earlier, and there's plenty of evidence (rather than proof) that Emily is indeed a ghost.
The fact that Revolution has confirmed this leaves no doubt (at first I though that turn was an animation glitch!) and especially when you see a ghost in the next segment with Nico in the abandoned Underground station.