The 13-year-old singer agreed with judges Simon Cowell and LA Reid, who criticised her performance of Cyndi Lauper's 'Time After Time' during Diva Week.
LA Reid said of her performance: "I don't think it was the greatest song choice, because it didn't allow you to peak. You didn't get a chance to show your chops as well as I know you can. It was the song's fault, not yours."
Simon Cowell agreed with Reid, adding "I thought the song was boring. It just went on and on, so it's song choice. For some reason, Britney isn't quite getting the right songs for you."
Spears intervened: "Simon, she has more talent in her pinky than all of your contestants together."
Demi Lovato added: "I liked the song choice, because I think it really showcased a different side of you that we haven't seen. Your voice, I didn't know that you could sound so soulful and your tone is incredible. You did amazing."
On her song choice, Miller told E! Online: "I don't really like slow songs. I listen to Nirvana and Radiohead, not really the divas.
"My song was really boring, and I've been telling Britney that from day one. She just said, 'Get through it and try to connect with the song'. I don't think it really mattered to her that I didn't like it."
Watch Beatrice Miller's performance of Cyndi Lauper's 'Time After Time' below: