Morris was born in Connecticut and raised in Trumbull. She recalls her first-ever voice-over role as recording for an English as a Second Language learning cassette when she was 12. Her parents would occasionally pull her out of school to take her to auditions in New York City. When she was in middle school at around age 14, she was involved in an educational video series called Real World Science where she served as the on-screen program host as well as provide narration for the science videos being presented. She described her experience as good practice reading scripts, and noted that the producers at Mazzarella Media kept calling her back to do more videos, so she continued working on those through high school and college, where she would later help the company in production and script writing for other educational videos. She got involved in journalism when she wrote for the local newspaper The Trumbull Times where she covered high school sports. She graduated in 2004 from New York University with a B.A. degree in Journalism and Mass Communications. In New York, she wrote for US Weekly magazine, New York Press, The Aquarian and Metro New York. She also worked as an associate producer and blogger on Cool in Your Code, a local television show that covered a different New York City zip code every episode. In 2010, she moved to the Los Angeles area, wrote for Patch.com, served as a blog writer and editor in the Prom and Formal Dances at About.com, and wrote blog articles for David's Bridal.
While in New York, she got involved in voice acting at 4Kids Entertainment and NYAV Post with English parts in anime dubs. Her first ever anime role was in Magical Doremi, which did not air on television, and her first anime television role was with Yu-Gi-Oh! GX where she voiced Alice, and later Yubel, which was her first major anime role. In an interview she said that she would get instructions on how to voice the character based on a brief description and sometimes a picture of the character. Prior to voicing in anime, she was only aware of a few titles such as Dragon Ball Z which her brother liked, and Sailor Moon which her friends liked. She said "It's surreal because I took the original role (in Yu-Gi-Oh) because I liked the character and, of course, as an actor you want to work, but it came with this bonus of all these fans. It's amazing to be part of such a close-knit excited community." She would later voice in Pokémon as well as cartoons such as Winx Club and Chaotic.
Morris would continue voice acting in Los Angeles. In 2011 she got a starring role of Ritsu Tainaka, the drummer and outspoken character in the girl band anime K-On!. She voiced the role of Saki Mikajima in the Durarara!! series which aired on Cartoon Network and which had a sequel in 2015. In 2012, she voiced Kyubey, the mascot character in the magical girl drama Madoka Magica; she says the Kyubey was one of the most controversial anime characters, and made people react strongly. In Sword Art Online, released in 2013, she voices Leafa. The show was broadcast on the Toonami block of Adult Swim, and ran for two seasons. In the romantic comedy Toradora, released in 2014, she voices Taiga Aisaka, the lead heroine who pairs up with a guy in order to court his best friend while he courts Taiga's best friend. She liked playing the tsundere personality of Taiga. The show was one of the first anime to be dubbed and released by NIS America. In 2014, she voiced Sue in Doraemon: Gadget Cat from the Future, the English dub of Doraemon which broadcast on Disney XD.
In the anime film Oblivion Island: Haruka and the Magic Mirror, she voiced Teo, the co-lead to the title character. She also voiced the title character in Patema Inverted, a film where her character discovers a world where everything is upside down and gravity causes her to fall to the ceiling of a room. Other anime film roles include Akiko in Time of Eve, Noriko in Welcome to the Space Show, and Natsuki in Psychic School Wars.
In cartoons, she provided the voice of Lola, one of the three main kids in the cartoon series Angelo Rules which was run on Cartoon Network as well as Netflix. She voiced Bubbles in the Netflix cartoon series Popples, based on the toys of the same name. She provided the voice of Frankie Stein in the Monster High reboot film, Welcome to Monster High.
In 2011, she voiced the title character Totoria, an alchemist, in the role-playing video game Atelier Totori: The Adventurer of Arland. Gadget Review, in reviewing the game, said that normally they would ignore the English dub adaptation for a Japanese game, but liked the English voice actors, calling them full of emotion and "always delivering their lines the way you think they should". The reviewer from The Otaku's Study found the English voice-acting for the female characters to be strong, and that she "portrayed the innocent character role effectively." Travis Bruno of Capsule Computers in Australia said that the dub "continues to impress". Morris would reprise her character in Atelier Meruru: The Apprentice of Arland, where Totori was Meruru's mentor.
In the fantasy role-playing video game Bravely Default she plays main party character Edea Lee, who she describes as a "tiny, spunky, badass warrior." and likened her to herself if she were placed in a medieval setting. She reprised her character in Bravely Second. Jason Hidalgo of Reno Gazette-Journal found the English dub to be hit or miss, but "thoroughly enjoyed Edea’s hilarious 'Mrgrgr' commentary."
In Xenoblade Chronicles X, she voices Lin Lee Koo, one of the main characters in the story. She auditioned and won the role despite the only direction she was originally given was that the video game involved "space travel". Morris sought to preserve Lin's characteristics as strong female figure in her portrayal, describing her as "super smart and very self-reliant... She can cook dinner and also kick your ass." Morris's take on the character did however include using a deeper, older-sounding voice for Lin, partially to accommodate for the age change, and partially because it was believed that Western audiences would find the high-pitched Japanese version "grating". She voiced between 1,600 and 1,800 lines of dialogue for Lin – above average for a video game. In response to a controversy over Lin's bikini costumes being more covered up in the North American and European versions, Morris said that it bothered her that Lin was only 13 years old, but sees the censorship more as localization and that it would make the game open up to a wider audience.
In Persona 5, she voices Morgana, a shapeshifter character that appears as a cat during the day and guides the main character and his team through the world of shadows. Morgana was described as the mascot character of the game, which meant some "heavy pressure" for Morris as a main character in the series.
Morris has narrated a number of audiobooks, a few of which have earned her AudioFile magazine's Earphones Awards, the first was for the young adult novel Dear Zoe by Philip Beard in 2004. Other Earphone Award-winning titles include Salt to the Sea by Ruta Sepetys, Pip Bartlett's Guide to Magical Creatures by Jackson Pearce, and The Tapper Twins Go To War (With Each Other) by Geoff Rodkey. The audiobook The Elegance of the Hedgehog by Muriel Barbery, where Morris voiced the 12-year-old Paloma, won AudioFile's Best Audiobook of the Year and Publishers Weekly's Listen Up Award. Her narration of children's book A Snicker of Magic by Natalie Lloyd received a nomination at the 2015 Audie Awards and received the Honor Recording Odyssey Award from the American Library Association. Morris said that she has worked on many audio books for Simon and Schuster's Books For Young Readers series, where she would record at her studio in Los Angeles and would be patched over by phone line to her producer/director in New York.
Morris married songwriter and producer Steve Shebby on February 13, 2016. They live in the Los Angeles area.