Castillo has championed the rights of nurses in her nearly two decades with NNU and has been a vocal advocate for creating federally administered national health insurance. In January, she organized events across the country calling for increased safe-staffing investments by healthcare organizations. In May, Castillo testified at a Senate hearing in support of Medicare for All legislation, highlighting the impact of Covid-19 on the nursing industry and criticizing the current system as “profit-driven and fragmented.” NNU has more than 175,000 members. Before Castillo’s current job, which she has held since 2018, she was the director of the Registered Nurse Response Network, a disaster relief program run by NNU.