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In case you missed it -- there was a lot of speculation last week that Rihanna dissedKarrueche Tran on Twitter -- posting a pic of a bag of rice cakes wearing sunglasses ... with the caption, "Ima a make u my bitch."
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But several of Rihanna's fans took the joke one step too far -- unleashing an avalanche of violent threats on Karrueche ... like "I hope Rihanna beat the dog shit outa yo ass!" ... "Watch yo back" ... and "I will kill you."
Rihanna never admitted the rice cake jab was directed at Karrueche -- but sources close to Karrueche tell TMZ, she now refuses to leave her house without Chris Brown's hired muscle by her side.
As for Karrueche's infamous BF -- we're told CB is 100% supportive of his new lady ...despite getting close with Rihanna recently ... and is urging her not to worry.
The real lesson here -- don’t date Chris Brown.