Mamun competed at her first Senior Europeans at the 2013 European Championships in Vienna, Austria and together with her teammates (Yana Kudryavtseva and Daria Svatkovskaya ) won Russia the team gold medal. At the event finals, she won gold in ribbon and three silver medals (ball, hoop and clubs). She then competed at the 2013 Summer Universiade, where she won gold in All-around ahead of teammate Alexandra Merkulova. At the event finals, she won gold in hoop, ribbon, clubs and placed 8th in ball.