Mumy starred as Roxy in the series Winx Club: Power of Believix in 2012 and voiced the role of Leni in the series The Loud House in 2016. Since 2012 she has voiced the role of Beth Tezuka in the television series Bravest Warriors. She has also starred in or voiced roles for the films The Santa Clause 2: The Mrs. Clause, Lilo & Stitch, Cheaper by the Dozen, The Santa Clause 3: The Escape Clause, Snow Buddies, Space Buddies, Santa Buddies, and Batman: Year One. Mumy won a Young Artist Award for Best Young Ensemble in a Feature Film for Cheaper by the Dozen in 2004. Her father is actor Bill Mumy.