The teenager's winner's song became available to pre-order on the high street store's website before Little Mix and Marcus Collins's were available, causing outcry from fans who believed that it was fixed for her to win the ITV talent show.
Speaking about the fiasco, Lily said: "Well, when me and Kelly found out about the HMV thing, we were really upset about it. But it's made me more determined to go out there on Saturday and give it even more than I gave before.
"People have their opinions and say that it's a fix. But it's not. It was a mistake, it couldn't be helped and accidents happen."
Gary Barlow joked: "Good publicity for HMV."
Promoting her one act in the final, judge Kelly Rowland described Lily as "a beast".
"She's been beasting ever since she got here... period," said Rowland. "The most amazing thing about Amelia is her work ethic. That's what so admirable about Amelia. Every time she performs she wants to make it better than the last and she's thinking in her head about how she can be better next time."
The X Factor final kicks off on Saturday (December 10) at 8pm on ITV1.
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