Rial was born in Houston, Texas. Her father is from Pontevedra, Galicia, Spain. When she was young, her family would often visit Spain. She would translate for her younger brother some of the European Spanish-dubbed cartoons which included anime shows Doraemon and Dragon Ball Z, often imitating the various characters. She studied ballet, tap, and jazz, but transitioned to musical theatre when was 12. She studied acting through high school as well as college at the University of Houston. In an interview with Otaku News, Rial mentioned voice actor inspirations from The Simpsons, Family Guy and Beavis and Butt-head. She was working on a theatre show with Jason Douglas, who suggested she audition for ADV Films. Her first voice-over role was some walla in the 1999 dub of Martian Successor Nadesico. In an interview with Otaku News, Rial said she had to talk for two minutes straight as folks in a crowd telling the Jovians to go home. She would later land main character roles as Miharu in Gasaraki, Natsume in Generator Gawl, and the title character in ADV Films’ production of Hello Kitty’s Animation Theater, the last of which one of ADV’s best-selling DVDs. In 2001, she voiced Izumi in the baseball anime Princess Nine and in 2002, she got to voice Hyatt in Excel Saga, which she listed among her absolute favorites.
In 2003, she voiced best-friend character Kyoko Tokiwa in Full Metal Panic!, and got to reprise her for Full Metal Panic? Fumoffu and Full Metal Panic: The Second Raid. She voiced Kirika Yuumura, the quiet assassin partner in Noir. Rial said that Kirika was challenging because she had very few words but had to convey a lot of emotions. She also noted that Kirika’s personality changed over the course of the series, so she voiced her to be more emotional in later episodes which drew some criticism from fans. She also voiced Lila in Najica Blitz Tactics where she also got to do a DVD commentary along with fellow actress Kira Vincent-Davis. The commentaries have become popular as she receives feedback from fans about them at anime conventions. She voiced female protagonist Haruka Shitou in the sci-fi show RahXephon.
Rial started voice-over work with the anime dubbing company Funimation in the Dallas/Ft. Worth area. In 2004, she voiced Amy in the long-running detective anime series Case Closed, and Lyra (aka Dante) in the drama series Fullmetal Alchemist. Both of these shows were featured on Cartoon Network. She also voiced co-lead character Lumiere in Kiddy Grade. Meanwhile, with ADV, she voiced Nyamo-sensei in the school comedy Azumanga Daioh. She had also taken over some character roles as Momiji in Blue Seed and Maya in Neon Genesis Evangelion. Rial said that it was very difficult to try to sound like the previous voice actors, especially Maya’s low voice, so she tried her own approach. She also got to voice Pen-Pen the penguin in Evangelion. In 2005, she voiced the serious lead character Jo in a team of mercenary girls in the cyberpunk science fiction series Burst Angel.
Rial continued to land leading roles in anime shows. In 2006, she voiced the title character in Nanaka 6/17, about a 17-year-old girl who through an accident, has amnesia and regresses to her 6-year-old self. In Speed Grapher she voiced female protagonist Kagura Tennōzu, and in the ADV Films remake of Macross, she voiced Misa Hayase. In 2007, she voiced Sakura in the English anime adaptation of Clamp’s Tsubasa: Reservoir Chronicle; Maria in Witchblade; Misuzu Kamio, a heroine in Air, and the title character in Kurau: Phantom Memory. She also voiced lead characters Misao Shinohara, Sasami’s best friend in Sasami: Magical Girls Club; and heroine Asa Shigure in the harem comedy Shuffle!.
In 2010, when Dragon Ball Z was remade as Dragon Ball Z Kai, Rial got to voice the heroine character Bulma. She voiced other lead girl characters in Sekirei, Soul Eater, Fullmetal Alchemist Brotherhood, and Casshern Sins. Both Soul Eater and Brotherhood have had sizeable runs on Adult Swim’s Toonami block. She voiced the title character Mina Tepes in Dance in the Vampire Bund, as well as several lead female characters in ensemble shows Rosario + Vampire, Highschool of the Dead, and Fairy Tail in 2011.
Rial voiced more leads in 2012 with Shiro in Deadman Wonderland which also broadcast on Adult Swim, Stocking in the raunchy comedy Panty & Stocking with Garterbelt. In 2013, she voiced the heroine character Haruko Amaya in the harem comedy Maken-ki! and Iori Nagase in the school anime series Kokoro Connect. With regards to her lead role of Michiko Malandro in Michiko & Hatchin, which was released on DVD in 2013 and was broadcast on Adult Swim in 2015, Rial said that out of the 300 or so characters she had voiced, only two of them were Hispanic, and she liked that her character wasn’t a stereotype. In 2014 and 2015, she voiced the title characters in the comedies Watamote and Maid Sama!.
In addition to voice acting, Rial has been steadily involved in ADR script writing, with work in the English dubs for D.N. Angel, Madlax, and Gatchaman. In an interview with Active Anime, Rial said she would “take the direct translation and write it into a coherent scene that matches the lip flaps”. At later anime conventions, Rial has mentioned that ADR script writing has kept her quite occupied, especially with “broadcast dubs”, that is, shows that are locally dubbed soon after the original broadcast. She has also written columns for Newtype’s USA edition.