EXCLUSIVE

Mariah Carey's former manager -- the woman who fiercely protected her and managed numerous crises -- has sued her... TMZ has learned.

Stella Stolper has filed legal docs stating that a lawsuit is about to be filed against Mariah for violation of the U.S. Civil Rights Act, a Violation of the Fair Employment and Housing Act as well as breach of contract.

Our sources say the suit involves a huge amount of money Stolper claims Mariah didn't pay her, but it involves more than money.

Stolper and Mariah were once joined at the hip until Carey cleaned house around a year ago. Stella was Mariah's go-to person during her turbulent engagement with James Packer.