It's illegal to sell organs that have been donated, and all the girl's family have to do is say they do not choose to donate.
Many things are illegal, but are done anyway. For the right kind of human organ, the black market might pay between $30k and $100k. That’s more than enough to tempt the unscrupulous.
Hospitals and other authorities have also been known to destroy critical parts before autopsy, to cover their rear ends against lawsuits.