Reality Check! Inside Why Mariah Carey Really Split With Her Fiancé

Mariah Carey's world is crashing down around her — and it's all because her billionaire fiancé James Packer has dumped her flat!

The Australian tycoon, 49, has walked away from diva Carey, 47, because he's so fed up with her expensive tastes and her obsession with her new reality TV show, according to RadarOnline.com sources.

Notoriously private Packer fell head-over-heels for Carey in 2015 after they met at one of her Las Vegas shows, but sources reveal the pair has been at odds for months because of Carey's lavish lifestyle and how she always puts her career and image ahead of Packer and his family.

The upcoming premiere of her reality series, Mariah's World, "was the last straw," said one snitch. "The closer they got to premiere day — December 4 — the worse things got between them. And it doesn't help that Mariah's still close to her ex, Nick Cannon."

Packer was irked by Carey's refusal to attend a birthday party for his sister, Gretel, and Packers' mom failed to connect with the songbird, sources noted.

Carey and Cannon were looking like quite the cozy family with their 5-year-old twins, Monroe and Moroccan, at her star-studded Oct. 22 Halloween bash. But Packer was a no-show at the same Halloween festivities — a major relationship red flag.

So far, Carey's keeping her $10 million 35-carat diamond engagement ring. Her rep insisted, "They're trying to work it out."

But the pair have not seen each other for more than a month after their spat in Greece that the rep insisted was not over Carey's spending.