By sarcastically pretending that this 16-year-old made an affirmative choice to become a parent, the parent is actually trying to shame her for having sex as a teenager.
This goes directly to the heart of the article's point. Rather than confront a system that places some people at a disadvantage (lack of access to birth control or childcare), it's easier to insinuate that a person's hard life is solely the result of their own bad decisions.