Lehis began fencing in 2004. Coached by Helen Nelis-Naukas and Peeter Nelis, she was a member of the Estonian Junior and Cadet fencing teams since 2009. In 2014, Lehis won individual gold at the Junior World Fencing Championships and was named Estonian Young Athlete of the Year. She won team épée silver medals at the 2015 European Fencing Championships and the 2015 European Games. In 2018, Lehis won the individual gold at the 2018 European Fencing Championships. At the 2020 Tokyo Summer Olympics, she won a gold medal in team épée and bronze in individual épée.