Briana is Kaley's assistant, but the actress urged her sibling to pursue her dreams and convinced her to audition for the singing competition.
During her sister's performance, cameras showed "The Big Bang Theory" star and her mom backstage shouting at the judges to turn their chairs around for Briana.
Briana sang a rendition of Lady Gaga's "You and I," and after some deliberation, Christina Aguilera turned her chair around to face the performer. Cee Lo Green also vied to get her on his team, but Briana opted for "girl power" and picked the pop starlet to be her mentor.
Watch Briana's performance and Kaley's reaction below: