Maria is a hands-on mum to Patrick, 21, and her other three children with Arnold Schwarzenegger - Katherine, 24, Christina, 23 and 17-year-old Christopher – but she trusts their choices, the insider added.
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Maria Shriver is said to be 'happy' about her son's new romance
She is also said to have spent time with Miley in recent weeks, and gotten to know the singer.
A source had previously told Hollywoodlife.com that Maria is "very, very worried about the influence Miley's having on Patrick".
"She fully believes that you become who you surround yourself with and she's always been so happy with the friends Patrick chooses, she never saw this coming."
But it seems those reports were unfounded, and Maria has given her blessing to Patrick and Miley's romance - which seems to be going from strength-to-strength. The couple, rumoured to have been dating for a few months now, jetted out of LA together on Tuesday on a private plane bound for Miami.
Patrick Schwarzenegger and Miley Cyrus' relationship is going from strength-to-strength
Shortly before that, they partied together at Miley's 22nd birthday party in Malibu – and Patrick was by her side all night. "They were cute and affectionate together," an onlooker told People. "Patrick seems extremely happy."
A source recently confirmed to E! News, "This is more than just a fling. They look like they are falling in love with each other."
In fact Patrick has been smitten with the former Hannah Montana star for some time now. In 2011, he said his "girls for the future" included Selena Gomez and Kendall Jenner, but concluded, "My eye, though, is set on Miley."