Ellona Santiago stunned all four judges with her performance of Jessie J's Mamma Knows Best, which she sang for her older sister on Wednesday night's X Factor.

The 17-year-old entered the stage wearing a white blazer, high heels and a Fedora, as she powerfully belted the song's lyrics. The young contestant then took off her blazer and dominated the stage in a short gold dress.

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Santiago received a standing ovation from all four judges - Kelly Rowland, Paulina Rubio, Demi Lovato and Simon Cowell. Rowland told Santiago it was her "best performance" yet, while Rubio called her a "leader." Cowell also expressed his satisfaction and said the performance was a "game changer."

"You may now have a chance, after that performance Ellona, of actually winning this whole show," Cowell added. "And, by the way, Ellona, I want to send my love to your sister, she's a fantastic girl."

Santiago performed the impeccable rendition on the pre-Thanksgiving episode in honor of her older sister, whom Cowell was referring to.

"I'd really love to dedicate this song to my sister," Santiago said in a video aired before her performance. "My eldest sister, Julie Rose, is like my second mom. She was always here for me. I've actually never really thanked her for everything that she's done for me and recently, she just got diagnosed with stage four cancer and it hurts because sometimes I just want to be there for her and I'm here."

Julie Rose then surprised her little sister and showed up at Ellona's rehearsal to give her words of comfort.

"I'm continuing to fight," she told her. "You need to do the same thing."

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