She signed with Viva Records in 2004 and released her self-titled debut studio album, supported by the cover single "Don't Cry Out Loud".

[10][12] The Philippine Star critic Matthew Estabillo praised her vocals and stage presence, highlighting Go's win as one that did not rely on the sob stories frequent in reality shows.

[10] Reviewers from The Philippine Star lauded Go's vocal range and were impressed with the overall production; Baby Gil complimented her "natural R&B groove", and a writer deemed it a well-crafted album.

[15] In July 2004, Go was a co-headliner, along with Sarah Geronimo and Erik Santos, for Night of the Champions at the Araneta Coliseum;[16] the production won Best Major Concert Collaboration at the 2005 Aliw Awards.

[25][24] Gil from The Philippine Star felt that the album illustrated a "unique mixture of Filipino sensibility and cosmopolitan flair", and noted how Go continued to improve and refine her music.

[28][29] The album was described as a "hodgepodge" of wide-ranging global influences, and Go again employed the help of De Walden, who oversaw the collation of its content, as well as Jimmy Borja, Tony Ramirez, and other songwriters based in Europe and the United States during production.

[28][29] A second single, "Alam Ng Ating Mga Puso", was released in May 2007;[31] and with Christian Bautista, she recorded the duet "Pag-ibig na Kaya", the theme of the Filipino-dubbed South Korean television series Princess Hours.

[34][36] The Philippine Entertainment Portal journalist Bong Godinez wrote that the album is more "proof of [her] willingness to take risks and at the same time brandish her flexibility as a singer".

[39] A tribute album, it included her versions of music from the 1970s and 1980s such as Taylor Dayne's "I'll Always Love You", Harold Melvin & the Blue Notes's "If You Don't Know Me by Now, and Bread's "If".

[44] Released in October 2011, Unbreakable featured the single "Whispered Fear", a song she had developed four years prior and one she regards as a lyrically personal output.

[46] It tells the story of a teenager (played by Barbie Forteza) of African American heritage, exploring issues of systemic racism and the demeaning treatment faced by people of color.

[48][49][50] She then became a mentor in the reality singing talent show Protégé: The Battle for the Big Break (2011) alongside Janno Gibbs, Jaya, Jay R, and Aiza Seguerra, among others.

[51] Also in 2011, Go made her theater debut in the local production of The Little Mermaid, playing the lead role of Ariel, the titular character based on the 1989 animated film adapted from Hans Christian Andersen's 1837 fairy tale.

[55][56][57] In a review of the opening night, the Philippine Daily Inquirer writer and singer-actress Lea Salonga deemed Go excellently cast for the part, adding that her singing was a "great mix of that clean and pristine Disney sound".

Set during the pre-colonial era of the Philippines, the show featured flight sequences, requiring her to perform stunts while strapped into harnesses; the project was the most expensive series by GMA Network at the time.

[65][66] Kaye Estoista-Koo of the Philippine Entertainment Portal termed Go's portrayal as "super cheery and upbeat",[65] and Rappler's Pia Ranada took note of her emotional delivery, but was critical of her British accent use.

[67] Go's international breakthrough came in 2014 when she starred as Gigi Van Tranh in the West End revival of Claude-Michel Schönberg's and Alain Boublil's musical Miss Saigon.

[76][77] After her work with Miss Saigon finished in 2015,[78] Go next played Fantine, a prostitute dying of tuberculosis, in Les Misérables at London's Sondheim Theatre.

[84] Later that year, Go recorded a version of "A Dream Is a Wish Your Heart Makes" for the Asian release of the live-action film Cinderella (2015), which premiered on Disney Channel Asia.

[88] It received favorable reviews,[89] with Marilyn Stasio of Variety praising Go's convincing performance and how she stood out in the part,[90] and David Rooney of The Hollywood Reporter complimented her as an excellent vocalist.

[97] Writing for Newsweek, Tufayel Ahmed asserted that she "gives a mesmerizing performance ... shows powerful range, from an innocent naivety ... to a woman more pained and tragic".

[102] In December, she returned to playing Fantine at West End's Les Misérables before its postponement due to the outbreak of the COVID-19 pandemic;[103][104] she resumed her role when the production reopened and also had a limited run for the show's concert edition in 2021.

When the two performed together during the 25th anniversary gala of Miss Saigon at London's West End in 2014, Go described it as a childhood dream fulfilled;[114] she credits Salonga as someone instrumental in her decision to undergo auditions for the musical.

[35] For her cover album Falling in Love, she curated a catalog that incorporate influences of 1970s and 1980s music from artists, including Petula Clark, Dennis Lambert, Helen Reddy, and the Hues Corporation,[40] describing these as a reflection of her life and frame of mind at the time.

[125] Emmie Velarde, a journalist with the Philippine Daily Inquirer, highlights Go's tone and power as one with "formidable sharpness", writing that her range "hits impossibly high notes in as many different ways as she pleases ... alternately with grace, with authority, at times with something approximating vengeance".

[40] After Go's musical transition to theater in 2011,[127] reviewers appreciated her clear and sweet-sounding vocals, complimenting her sense of pitch in her portrayals of Disney Princesses Ariel and Jane Porter on stage.

[90][91] In a review of West End's Hamilton, Newsweek critic Tufayel Ahmed commended Go's strong vocals and range,[98] and The Observer writer Susannah Clapp lauded her "full-throttle", empowering belting.

[f] A reviewer from The Philippine Star characterized her debut album as an exploration of musical styles, with songs that identify as "bittersweet ballad", "inspiring anthem", and "hip hop dance", among others.

[132] From 2008 to 2011, she was romantically involved with high-profile personalities, including dancer Gab Valenciano, former Callalily lead vocalist Kean Cipriano, and actor John Prats.

[45][133] In February 2017, Go moved to New York City for Miss Saigon's Broadway revival, and met American luxury fitness executive Martin Spies.