Born in Rockhampton, Scarlett's parents enrolled her in singing and dancing lessons at the age of four. She later took speech and drama lessons and went on to complete her Trinity and AMEB Classical Voice and Speech/Drama Examinations as well as her RAD and Cecchetti Classical Ballet Examinations.
Growing up in central Queensland with her five brothers, Scarlett's family moved to Sydney when she was 15 to attend Newtown High School of the Performing Arts. After attending NSHPA for five weeks, she was offered a scholarship to study full-time classical ballet. She went on to complete her ballet scholarship, but after suffering stress fractures, realised she did not want to concentrate on classical ballet alone, but wanted to sing and act as well. After finishing her senior schooling, Scarlett began studying a Bachelor of Medical Radiation Science in Nuclear Medicine at the University of Sydney. However, during her first year, she chose to audition for the Western Australian Academy of Performing Arts (WAAPA). She graduated from WAAPA in 2008 with a Bachelor of Arts (Music Theatre). She received the Finley Award in 2007, and the Leslie Anderson Award for the best overall Showcase Performance and the Hal Leonard Award in 2008. Whilst at WAAPA, Scarlett appeared in several shows and played the leading role of Mrs Johnstone in its 2008 production of Blood Brothers.
Scarlett was cast in the 2009 Australian Tour of Breast Wishes, making her professional debut in the role of Sal. Scarlett was then cast in the ensemble in the 10th Anniversary Tour of Mamma Mia!, and understudied the main juvenile roles of Sophie, Ali, and Lisa. She then joined the ensemble cast for the 2010-2012 Australian and international tours, performing the role of the witches' mother and understudying the roles of Elphaba and Nessarose. Scarlett felt as though she had become "a professional understudy".
In 2013, after a series of auditions, Scarlett was cast in the lead role of Sandy Dumbrowski in the Australian production of Grease opposite Rob Mills as Danny Zuko. Producer John Frost noted that Scarlett "came in and auditioned and she just knocked us away, so this is a great opportunity for her". The production opened on 25 August 2013 at the Lyric Theatre, Brisbane, to strong reviews. In December 2013, Australian producer John Frost announced that Grease would extend its Australian tour to include Singapore, Perth and Adelaide in 2014. This will be Scarlett's first return to Perth in a starring lead role. Grease continued its Australian tour to Hobart in September 2014 and will return to Melbourne at The Regent Theatre in December 2014. Scarlett will remain in the lead role of Sandy.
Between seasons of Grease, Scarlett was cast as 'Sally' in the world premiere concert of Matthew Lee Robinson's Happy People at Melbourne's Chapel off Chapel on 18 and 19 October, starring alongside Bobby Fox (Jersey Boys), Tom Sharah (That ‘90s Show), Sun Park (Mamma Mia!), Bert LaBonté (The Mountaintop) and Robyn Arthur (The Boy From Oz), with direction by Chris Parker. The show received positive reviews, and Gretel Scarlett was received positively for demonstrating her versatility to what most Australian audiences have been unaware of. One reviewer stated "Scarlett as the manically cheerful Sally shows off some fantastic comedic chops, as well as her stunning voice of both range and power" and Sun Herald theatre critic, Simon Parris, stated she showed "a far deeper level of talent than she is able to demonstrate when performing the simple level of direction she has been given in Grease. Looking absolutely gorgeous as the Barbie-like Sally, Scarlett enhances the character’s Pollyanna outlook with a delicately vulnerable undercurrent. Her performance of “Nice” is nothing short of sensational."
In April 2015, Scarlett was cast in the leading role of Kathy Selden, to play opposite Adam Garcia, in the 2016/2017 Australian touring production of Singin' in the Rain. The show begins rehearsals in March 2016, and is set to open at Her Majesty's Theatre, Melbourne in May 2016. The tour will follow with seasons from July at Sydney’s Lyric Theatre before touring to Brisbane QPAC, Adelaide and Perth. On August 1st, it was announced that joining Scarlett and Garcia, will be fellow Australian performers Erika Heynatz and Jack Chambers.
On Sunday 13 December 2015, Scarlett will be co-hosting and performing at the Sydney Adventist Hospital Carols by Candlelight, which will also feature Sam Moran, as well as the winner of The Voice Australia, Ellie Drennan.
Scarlett has made appearances at the NSW Premier's Concert and Channel 7's Carols in the Domain. In 2011, she was selected as one six finalists in the Third ANZ Trustees Rob Guest Endowment Award, performing live at the gala concert at Her Majesty's Theatre, Melbourne. In 2013, Kristin Chenoweth unexpectedly invited Scarlett onstage to sing a duet of "For Good" with her from the musical Wicked. Dubbed by one reviewer as "the showpiece of the entire night", the performance brought "a mid-show standing ovation from the delirious crowd."
Scarlett has appeared on Channel 9's Today show as well as Channel 9 Mornings. In June 2013, Scarlett was invited to sing the Australian National Anthem at Brisbane's Suncorp Stadium at game 2 of the 2013 State of Origin series. Scarlett has performed at the Helpmann Awards and at the 2013 Australian Children's Music Foundation, performing a duet with her Grease co-star Rob Mills.
In 2014, Scarlett announced that she was in the process of recording her debut solo album, featuring covers from The Rolling Stones, Queen, and Carole King. The album, titled Hopelessly Devoted, was electronically released on 15 September, and debuted at #54 on the Australian iTunes Charts, #16 in the Philippines and #25 in Singapore.2009: Hello Again (Darlinghurst Theatre), associate choreographer
2009: Breast Wishes – Australian original cast tour, lead role: Sal
2009: Mamma Mia! – ensemble and understudy Sophie Sheridan, Ali and Lisa
2010: Wicked – Australian tour – Witches Mother, ensemble, understudy Nessa-Rose
2011–2012: Wicked – Asian tour – Witches Mother, ensemble, Elphaba understudy and Nessa-Rose understudy
2013–2015: Grease – lead role: Sandy
2014: Happy People in Concert by Matthew Lee Robinson – lead role: Sally
2016: Singin' in the Rain – lead role: Kathy Selden
Hopelessly Devoted – debut solo albumAnyone Who Had a Heart
I Can't Make You Love Me
Hopelessly Devoted to You
Let It Go
Say Something (featuring Rob Mills)
No One But You (Only the Good Die Young)
Firework (featuring Suzie Mathers)
So Far Away/It's Too Late
We Found Love
Grease – Australian cast album recording 2013 (as Sandy)Opening
Grease is the Word (Ensemble Vocals)
Freddy My Love (Ensemble Vocals)
We Go Together
It's Raining on Prom Night
Hopelessly Devoted to You
Look At Me, I'm Sandra Dee (Reprise)
You're the One That I Want
Breast Wishes – 2012 original Australian cast recording (as Sal)Let's Not Talk
The Breasts Money Can Buy
Mills and Boon and Me
Boobies in the Eye of the Beholder
Ain't Got Nothin'
There's A Moment
It's All About Them (reprise)
Let's Not Talk (finale)