Mariah is said to think he owes her for uprooting her two children from New York to Los Angeles, so Packer could be near his own children.
The report claims Packer also made financial promises to Mariah during their romance, which she wants him to fulfil.
Then there is the cancellation of the South American leg of her tour, which Mariah's camp are blaming on the trauma of the 'dramatic fight' on a yacht in Greece which ended their relationship.
Mariah previously blamed the cancellation on promoters, writing on Twitter last week: 'Devastated my shows in Chile, Argentina & Brazil had to be cancelled. My fans deserve better than how some of these promoters treated them (sic).'
Not that Mariah was letting the stress of her break-up show on Thursday night, as she partied with her closest pals - including dancer Bryan.
Bryan is reported to be at the centre of the break-up, with James reportedly using his status to get him 'banned from Caesar's Palace', where the songstress has a residency.
For her night out Mariah was putting on a lot of front in a cleavage-baring bralet, making sure she stood out from the crowd in her racy look.
The itsy bitsy, lace-up number barely contained her curves and definitely ensured she made an impact on her night out.
Mariah also wore a long-sleeved black jacket, teamed with bold red leather trousers that hugged her hips.
The Hero hitmaker pulled the risqué look together with a pair of towering heels in a similar lace-up style.
Wearing her hair down in loose waves and accessorising with large silver hoop earrings, Mariah ensured she was perfectly put together from head-to-toe.
The pop diva seemed in great spirits following her sushi experience, showing no sign of heartbreak.
Seemingly intent on showing James what he was missing, the star looked carefree and happy as she left the venue with her entourage.
DailyMail.com has contacted representatives of both parties seeking comment on the latest revelations.
It has become a very messy and dramatic end to the love story between the 46-year-old singer and the 48-year-old businessman.
The couple have not seen each other in over a month after a fight while on a romantic European vacation, her spokesperson has said.
The pair's engagement unraveled during a stay on a luxury yacht in Greece in September.
TMZ reported Packer allegedly did 'something really bad' that involved Carey's assistant and there are other allegations about his behavior.
Her spokesperson denied speculation the split was over infidelity and insists the 46-year-old singer's excessive spending was not to blame.
'Mariah and James had a fight in Greece, and have not seen each other since. The fight was not because of any cheating allegations or excessive spending by Mariah,' her spokesperson told ET exclusively.
'James is one of the most successful businessmen in the world. They are trying to work it out, the spokesperson continued.
'Right now, they're not sure if they will stay together. They are discussing it, and plan to release an official statement together about their future.'
Allegations made about Packer's conduct on their Greece trip have branded 'simply untrue' by his camp.
Packer was noticeably absent from the Vision Of Love hitmaker's Halloween party over the weekend, where the star was seen posing for photos with her ex-husband Nick Cannon and their twins.
The break-up puts the producers of the singer's upcoming show Mariah's World in an awkward spot.
The show focuses on Mariah, but her relationship with Packer formed a major storyline.
The New York Daily News reported that producers were' freaking out' over the development.
A source also told UsWeekly Carey felt her fiance wasn't 'present' enough for her.
'James has not been present for her so she unfortunately couldn't make it work and had to leave him,' an insider said.
The split was first reported by Woman's Day's in Australia, with a family friend revealing: 'It's all over.'
The seemingly unlikely couple first set tongues wagging in June last year when images emerged of them holding hands strolling around the romantic island of Capri in Italy.
The pair then became engaged in January after a whirlwind romance.
The duo remained coy on the details of their impending nuptials, but Mariah did suggest that the wedding would be a low-key event rather than an ostentatious affair.
'I can't really talk about them right now because everything is still being figured out,' she teased, noting, 'I never said it was gonna be a big wedding', she told People magazine, earlier this year.
