She played for the Senior National Team at the 2008 Olympic Qualification Tournament in Japan. There her team ended up in fourth place, and did not qualify for the 2008 Summer Olympics. She then played in July with her National Junior Team, winning the silver medal at the 2008 NORCECA Junior Continental Championship U-20, and was elected Most Valuable Player, Best Libero, Best Digger and Best Receiver. Shortly afterwards Castillo claimed with her Senior Team the gold medal at the 2008 Women's Pan-American Volleyball Cup in Mexico as a sixteen-year-old. Later that year her team won the silver medal at the Final Four Cup, as she won the "Rising Star" award.