Anya’s Ghost by Vera Brosgol

Of all the things Anya expected to find at the bottom of an old well, a new friend was not one of them. Especially not a new friend who’s been dead for a century. Falling down a well is bad enough, but Anya’s normal life might actually be worse. She’s embarrassed by her family, self-conscious about her body, and she’s pretty much given up on fitting in at school. A new friend—even a ghost—is just what she needs.

Or so she thinks.