Marchi graduated from the University of Oklahoma with a degree in theater, and has been acting professionally since 2000. She got her start in voice acting in Fruits Basket as Motoko Minagawa, and has worked on and voiced for a number of American adaptations of Japanese animated shows, including Black Cat as Rinslet Walker, Soul Eater as Liz Thompson, Sekirei as Uzume, Heaven's Lost Property as Mikako Satsukitane, Panty & Stocking with Garterbelt as Panty Anarchy, Freezing as Rana Linchen, High School DxD as Rias Gremory, Witchblade as Masane Amaha and Death Parade as Chiyuki. She also writes the anime dub scripts and directs other Funimation actors.
In April 2013, Marchi joined The Funimation Show web series as a co-host.
In September 3, 2015, Marchi made her debut role for Sentai Filmworks as Neko Kuroha in Brynhildr in the Darkness.
In November 3, 2017, she also made her first non-anime role as Green Guts in Cartoon Network's OK K.O.! Let's Be Heroes.
