Mendes transitioned her career to film, taking on supporting roles in The New Romantic (2018), The Perfect Date (2019), and Palm Springs (2020).

[6] Due to her father's job and later her parents' divorce, Mendes moved 16 times growing up, but lived mainly in Florida.

[7] Mendes attended the Fine Arts program at the American Heritage School in Plantation, Florida, graduating in 2012.

[12] In 2016, Mendes was cast as "silver-tongued high school sophomore" Veronica Lodge in The CW's teen drama series Riverdale (2017–2023), a subversive take on the Archie Comics.

In 2020 she appeared in the critically acclaimed sci-fi/comedy Palm Springs, which premiered at the Sundance Film Festival and was released that July on Hulu.

[19] In 2022, she co-starred opposite Maya Hawke in the teen black comedy Do Revenge for Netflix earning critical acclaim.

"[22] In February 2024, Mendes starred as Ana Santos, an ambitious art world intern in the Amazon Prime romantic comedy film, Upgraded.

[29] In August 2024, it was announced that she has been cast as Teela co-starring with Nicholas Galitzine as He-Man for the upcoming live action movie reboot of Masters of the Universe.