The 28-year-old actress-singer took to Twitter to give the clue, reported Daily Mirror.
"I don't care.. What they're going to say.. Let the storm rage on.. The cold never bothered me anyway..." alongside a picture of her dressed in a princess-style floor length gown, similar to Elsa's signature blue frock.
The song was originally performed by Idina Menzel, who played Rachel's birth mother on the show.
Former Disney star Demi Lovato also covered the track, which scooped the award for Best Original Song at the Academy Awards.