The baby was nearly fully formed with a face, hands, feet, and a heartbeat that could have survived outside the womb. I implore you to go look up some photos of a 28 week fetus and I guarantee you’ll be surprised how much it looks like a normal baby.
You’re right, it’s not Facebook’s business, but this 17-year old and her mother sealed their fate when they used Facebook’s platform to discuss a crime. Facebook had a legal obligation to hand over those messages because they were served a valid warrant.