Casa started playing with Spain's youth teams at 15, winning a total of six medals from 2008 to 2012. She made her debut with the senior team in 2013, when she was 20 years old. She won the gold medal at the EuroBasket Women 2013. After participating in a few friendlies in 2014 and 2015, she played again official games in February 2018, when coach Lucas Mondelo called her up for the 2019 EuroBasket qualifiers. Up to February 2018, she had 24 caps with 3.7 PPG.