The Gloucestershire-born star, whose real name is Tahliah Debrett Barnett, was nominated for the coveted award following the release of her debut album LP1.
The 26-year-old stepped out to celebrate her nomination on Wednesday evening at the awards' launch party at The Hospital Club in London.
Tahliah celebrated her nomination at the Mercury Prize launch on Wednesday
Dressed in an eye-catching black jumpsuit, a grey blazer and wearing her fringe in Cleopatra-style braids, Tahliah joined fellow nominees Kate Tempest, Anna Calvi and Nick Mulvey.
According to US Weekly, Twilight star Robert, 28, has been dating Tahliah for weeks now and the couple were photographed together recently in New York City's East Village.
"Tahliah thinks he's unbelievably handsome," an insider told the publication, adding that the pair were introduced by mutual friends.
Robert and Tahliah in New York
Robert and Tahliah are said to have bonded of their shared love of music. Robert has composed his own music in the past and sung on Never Think and Let Me Sign, two songs that appeared on the Twilight soundtrack.
Tahliah will find out if she has won the Mercury Prize 2014 when the awards show takes place at London's Roundhouse on Wednesday 29 October.