Mariah Carey & James Packer in Settlement Negotiations

Mariah Carey was ordered out of the house she was sharing with billionaire James Packer, but she's staying put and demanding that he buy her an L.A. mansion as PART of a settlement in what has become a nasty breakup ... so say sources connected to Mariah.

Our Mariah sources say she doesn't blame the breakup on James ... she blames it on famed, former Scientology bigwig Tommy Davis ... who worked closely with Tom Cruise until Davis broke from the org.

Mariah believes Davis has had an extreme influence on Packer, whom they say has not been himself since Davis got in his ear. Our Mariah sources believe Davis poisoned the relationship, complaining to Packer he was spending an exorbitant amount on lavish gifts for her.

Other sources tell us Packer brought Davis in partially to help curb wasteful spending, and he immediately ID'd gifts to Mariah as prime examples. BTW, Davis played a similar senior role as Chief of Staff for Tom Barrack's private equity firm, Colony Capital. This situation became a very contentious thing between Davis and Mariah's manager, Stella.

One source pointed out that Mariah has a multi-million dollar home in NY.

As we reported, Mariah said peace out after an alleged incident on a yacht in Greece between James and her assistant. Our sources say when she returned, she was ordered out of their Beverly Hills home, but she refused.

TMZ broke the story ... Mariah is demanding $50 mil from Packer, partly because she uprooted her family to be with him in L.A. and partly because the breakup left her so distraught she had to cancel a leg of her tour.

We're told part of Mariah's demand is that Packer buy her a home in L.A.

Our sources say Packer is expected to respond to Mariah's demand Monday.