Nicki started going off on Safaree late Tuesday night ... accusing him of emailing her constantly and crying on the phone to her mother. In one vicious tweet she said, "Look what 'men' have become so that they don't have to work. Fathers pls stay in your sons' lives."
Sources connected to the exes tell us Safaree's lawyers contacted Nicki's camp Tuesday and issued a final warning about a lawsuit he intends to file. We broke the story ... Safaree feels Nicki owes him a a ton of cash for his contributions to 3 of her albums -- and says he can prove it.
We're told that's what set off Nicki ... and she strongly disagrees with Safaree's memory of how she became a star. As she puts it, "After I worked so hard for what I have, & shared so much, the greedy are never satisfied."
As for Safaree's lawsuit, Nicki hinted she's got one coming for him -- "Caught him stealing money and never prosecuted him!!!! Now I'm DOING IT. ENOUGH!!!!!!"
A rep for Safaree denies he stole anything from Nicki. He seemed unfazed by the beef Tuesday night at Blac Chyna's emoji launch party.