“He and Maddison have so much in common, they’re having a great time,” they add.
According to the insider, the pair are heading back to Australia for the holidays and staying with his brother Chris and his wife Elsa.
“Chris has already given Maddison the thumbs up!” says the source.
“To say they like each other is an understatement. She’s really gotten under his skin,” they add.
Miley, 26, in the meantime is said to be fuming and despite being publicly lovey dovey with Cody Simpson, behind the scenes she still misses Liam.
“She’s been drunk dialling him for a while, but now that he’s hooked up with Maddison, she’s calling him all hours and leaving him rambling messages!”
Earlier this week, Miley publicly hit out at Liam yet again.
The Wrecking Ball singer looks as if she might be trying to get the attention of her ex-husband as she took another swipe at him on Instagram.
"There are good people out there that just happen to have d**ks. I've only ever met one, and he's on this live," she said on an Instagram live, referring to her 22-year-old current flame, Cody Simpson.
"There are good men out there, guys, don't give up," she said as she live streamed a conversation with Cody, who had just landed in Sydney for an appearance on The Masked Singer as the Robot.
"You don't have to be gay, there are good people with d**ks out there, you've just got to find them. You've got to find a d**k that's not a d**k, you know."