Gregg DeGuire, WireImage
The 19-year-old pop star told "The Tonight Show" host Jay Leno that her 22-year-old "Hunger Games" hunk took her by complete surprise when he proposed after sitting in as she filmed her intimate Backyard Sessions videos.
One of the covers she performed was one of Liam's favorite tunes, "Lilac Wine," written by James Shelton in 1950, and originally sung by Hope Foye in the musical "Dance Me a Song."
"He asked me to marry him, like, 20 minutes later," Miley told Leno. "So while I was singing that, I had no idea ... [but] he was looking at me funny [while I was singing]."
Co-stars in the movie "The Last Song," Miley and the Australia-born actor first started dating while filming in June 2009. They have split and rekindled their romance twice since then.
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