(CNN) A Parkland school shooting survivor is calling for Melania Trump to fulfill her pledge to combat cyberbullying -- starting with her own family.

"Hey @FLOTUS you say that your mission as First Lady is to stop cyber bullying," 14-year-old Lauren Hogg tweeted Friday. "Well then, don't you think it would have been smart to have a convo with your step-son @DonaldJTrumpJr before he liked a post about a false conspiracy theory which in turn put a target on my back."

President Donald Trump's eldest son liked a tweet promoting a false conspiracy theory that claimed that Lauren Hogg's older brother, David, had been coached by his father -- a former FBI agent -- to speak out against President Donald Trump.

"The fact that Donald Trump Jr. liked that post is disgusting to me," David Hogg said on "Anderson Cooper 360" Wednesday.

In her tweets, Lauren Hogg said that Trump Jr.'s seemingly tacit endorsement of the conspiracy theory had "created a safe space for people all over the world to call me and my family horrific things that constantly re-victimizes us and our community."