Lehmann came to England at the age of 19 after making her professional debut at Swiss club BSC YB Frauen. In the WSL, the then-teenager signed for West Ham United and spent three seasons at the club. In between, she was briefly sent out on loan to Everton in 2021. With the Hammers, Lehmann finished as a runner-up in the Women's FA Cup in the 2018-19 campaign
The Swiss forward then signed for Aston Villa and spent the next three seasons before finally moving away from England and heading to Italy. While personally Lehmann did not have a great season and remained sidelined for quite some time with injuries, as a team, Juventus won the league title - marking the first major trophy of her career. After spending only a season with the Italian giants, the 26-year-old signed for Como on a three-year deal