A source close to the twerking "Wrecking Ball" singer tells Radar that Cyrus, 20, communicates with Wenner several times a day, claims the two are dating and although it's casual, the former Disney star is completely in lust with the new man in her life.
"She's definitely dating him," the insider reveals.
"Miley talks about how hot Theo is and how nice he's been to her. She's definitely completely in lust with him."
In fact, the source tells Radar that Miley even snuck out early from her "Bangerz" album release party in New York City on Oct. 8 to meet with Wenner.
"He didn't come to the release party, but she snuck out at one point and went and met him at The Plaza," the insider told Radar.
And the source hints that when a random bunch of flowers arrived at the event, they weren't from Cyrus' label or her producer Mike Will — and her smiles made it look like a romantic gesture from Wenner.
"She said she's never met anyone as sweet as Theo," the source added.
Wenner, 26, is the son of Rolling Stone magazine owner and chief editor, Jann Wenner — where Theo started as an intern before becoming a photographer for the magazine. He also dated actress and model Liv Tyler, 36, in 2011.