"I like being myself, doing my thing!" Cyrus, 15, told PEOPLE at the El Capitan Theatre, which had been closed off for blocks to accommodate thousands of fans lining the sidewalks around it.
"I'm so excited to be here. It's the first time I've ever been at my own premiere," she said.
The concert movie is expected to set box-office records, say industry analysts. It was already No. 1 on MovieTickets.com on Dec. 1 – the first week tickets went on sale – and sold more over that weekend, a spokesman for the Web site told the Associated Press.
On Fandango, the Miley movie accounted for 30 percent of all tickets sold, behind only Cloverfield. "It's the best-selling concert movie in Fandango's seven-year history," said company CEO Rick Butler.
Strong Role ModelsAlso at the premiere: celebrities whose kids are fans of the teen sensation. Speaking to PEOPLE, Ugly Betty star Vanessa Williams said Cyrus "has energy, is smart, is talented. She writes her own music, she records it. There's no tricks and she gives you your money's worth."
As a parent, Williams says about Miley's relationship with father Billy Ray Cyrus, "Watching the dynamic with her and her dad is amazing. She moves you."
Speaks Up About BritneyAt the premiere, Cyrus weighed in on the travails of Britney Spears, telling Extra, "I think that she needs help. If I didn't have [my family], I'd probably be in the same position."
For support, says Cyrus, "You just got to know who your true friends are, and I think, for me, [that] is my mom. If you have sisters, I mean any girls that are in your family, that can understand and relate to you, I think is the best."
But when it comes to herself, Cyrus tells PEOPLE, her real treat after being on tour for three months (and having to be in Las Vegas for a Friday night appearance): "I get to sleep in my own bed tonight."