Child abuse?

So I’m apart of a mom community on Tumblr, the social media site. A mom I follow has recently admitted in multiple posts to abusing her child. He’s 12 months (but much younger adjusted as he was born at 25 weeks). She says she knows it’s wrong but writes it off as her ppd and basically uses it as an excuse. I understand ppd can be dark but it doesn’t mean you can have a free pass to abuse your child. She said she just squeezes his arms intentionally very tight and sometimes shoves him very hard away from her and is in general very rough with him on purpose but “feels horrible after”. She herself calls it abuse. I want to report her to CPS but being it a social media site I don’t know her info. Just her first name and the state she lives in. How would I do this, does anyone know?