Millousi began the 2015 season by once again competing at the Cottbus World Cup. She did not make the beam final after only scoring a 12.466 in qualifications after an error. At the European Championships in Montpellier, Millousi made an error on the uneven bars and did not qualify to the final. After her disappointing European Championships, Millousi competed at the Baku European Games where she qualified to the all-around final. Next Millousi competed at the Hungarian Grand Prix, winning the gold medal on beam and the bronze medal on floor. Millousi ended her season with a disappointing performance at the World Championships in Glasgow performing on three events.