"I am fully committed to Hannah Montana. It's what gave me this amazing opportunity to reach out to so many people," Cyrus tells PEOPLE, adding, "I couldn't do it alone. We have an amazing cast that is so supportive, including my dad who has been there for me every step of the way."
Over the weekend reports circulated that Cyrus, 15, and her dad, Billy Ray Cyrus, have been causing drama on the Disney Channel set by coming to work late and openly talking about wanting to get fired. There were also rumors of a rift between Miley and her costar Emily Osment.
A Disney Channel rep calls talk of on-set squabbles "just gossip," while a source close to Miley Cyrus says: "It's a lot of craziness."
"Miley is really devoted to the show and she's really upset by the gossip," continues the source. "Miley is never late to work. Every minute of her day is planned out. When she's not shooting the movie or the series, she's recording the [Hannah Montana] soundtrack. She has a lot invested in Hannah Montana. It's not going away any time soon."
On set "they're like a big family," says the source. "Emily and Miley are like sisters. Occasionally they have disagreements but they make up and they never let it effect their work."
While Cyrus is no stranger to the rumor mill – she was recently spotted with aspiring country singer Justin Gaston sparking buzz about a budding relationship – "she's used to all of the gossip about her personal life, but when people are attacking her professionalism, it upsets her because she works really hard," says the source.
Production for the third season of Hannah Montana began last month and the network has the contractual option to film a fourth season in the future. Starting in November, new episodes will start airing including one in which Dancing with the Stars contestant Cody Linley will return as Miley's on-screen ex-boyfriend Jake Ryan.
"I'm really excited about our new season," Miley tells PEOPLE. "We are making great new episodes that I can't wait for our fans to see."
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