I looked at the picture using my eyes.

Are you serious? You determined she’s definitively <18 by looking at a photo of exclusively her body?

why would the face be blocked if she was a consenting adult?

You’d have to ask Pam Bondi. They redacted all sorts of things, with no explanation provided. It would be completely reasonable to block out the faces of any women who were not suspected of being involved in any way as not to drive unwanted attention.