How is a girl spine different than a boys?

Answer 1

Since girls are smaller in size than boys, typically, their spine is smaller as well (though not by much). If the girl has large breasts, there could be stress on the spine, contorting it, though this isn't usually an issue.

The simple answer is that, there's no difference from a biological point of view.

From a philosophical point of view, a girl's spine differs from a boy's spine in that one belongs to a boy and the other to a girl.