When her nation Greece hosted the 2004 Summer Olympics in Athens, Matsa made her Olympic debut as a 17-year-old, competing in two swimming events. She posted a FINA B-standard of 25.61 (50 m freestyle) from an Olympic test event at the Athens Olympic Aquatic Centre. On the first day of the Games, Matsa teamed up with Nery Mantey Niangkouara, Eleni Kosti, and Zoi Dimoschaki in the 4 × 100 m freestyle relay. She held liable for an early relay takeoff, when the Greeks had been disqualified from the heats. Nearly a week later, in the 50 m freestyle, Matsa placed thirty-third on the morning prelims. Swimming in heat seven, she edged out Trinidad and Tobago's Sharntelle McLean to pick up a seventh spot by four-tenths of a second (0.40) in 26.46.