Archaeologists know quite a bit about the cannibalized remains that they found in the well in Jamestown. They know she was a 14 year old girl, when she arrived at the settlement, where she came from and what she ate growing up, and that she was learning to sew based on groves in her teeth.
So why aren't they able to find her identity? I thought the ships going to Jamestown listed all of their passengers. If so, how many 14 year old girls arriving on a ship on X date could there be? Am I wrong about passenger lists?
You're not entirely wrong about passenger lists. In fact, you can look at the names of 104 Jamestown settlers here. Interestingly, they are several marked as "boy," but none marked as "girl."
As to why we don't know who she is, I would direct you to this website.
The relevant quote is: "We know so little about Jane because, like most women and children of the time, she was not recorded in the historical documents."
Now, the website above also speculates that Jane arrived on the ship the Unity. Here is a list of passengers on the Unity. You'll notice that sometimes, just families are listed, without the names of the wives/children. The first names of the women also aren't given. To the best of my knowledge, we don't know enough about Jane to say who she was married to/the child of/the servant of, and that's likely why we can't determine her exact identity.
Follow up/side note: I know nothing about this topic, what would be a good place to read about this bit of history, aside from any answers to come.