Miley Cyrus's new romance with Liam Hemsworth has left his ex-girlfriend devastated.

The "Hannah Montana" starlet – who has been dating the former "Neighbors" actor since they grew close on the set of their new movie "The Last Song" – has left Australian student Laura Griffin heartbroken by taking her "boyfriend and best friend."

The 19 year old wrote on her Facebook web page: "Liam and I have been inseparable since school. But it's Miley Cyrus. How can I compete?"

Laura blamed the "Hannah Montana" actress for the breakdown of her relationship with Liam and said the pair would still be together if it wasn't for Miley.

She told Australia's Woman's Day magazine: "He was my boyfriend and my best friend. There is no other reason why we would have broken up."

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The co-stars relationship came to light when they were spotted kissing on the set of their film. Actor Alex Emanuel said: "Miley jumped into his arms and threw her arms around his neck and kissed him and leaned back and he was dipping her. It was like a scene out of an old movie where the guy's getting on a train and they're saying their goodbyes."

Last month, Miley was locked in a bitter war of words with her ex-boyfriend Justin Gaston.

The singer-and-actress – who split from the underwear model in June after a year of dating – traded insults with him through cryptic messages on Twitter.

Justin wrote: "People mistake stupidity for bravery way too easily."

Miley quickly replied: "Yeah. I love when people mistake bravery with writing a few stupid tweets trying to make it seem like they don't care. You're afraid to love."

Earlier this summer, the Miley was also romantically linked to 22-year-old Steve Rushton, a former member of pop band Son Of Dork.