Chris Brown’s GF is scared to leave her house without bodyguards by her side -- and she's telling friends, it's all because Rihanna's crazy fans are threatening to kill her.

In case you missed it -- there was a lot of speculation last week that Rihanna dissed Karrueche Tran on Twitter -- posting a pic of a bag of rice cakes wearing sunglasses ... with the caption, "Ima a make u my bitch."

The joke -- Karrueche's Vietnamese ... rice cakes ... etc.

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.

Rihanna and Chris Brown have reconciled ... at least professionally ... because the former couple have collaborated on 2 brand new songs.

It's only been 3 years since Brown pummeled Rihanna's face during a late night argument in L.A. ... but the singer and her ex-con ex-BF have each released songs featuring the other's voice. One is a remix of Rihanna's song, "Birthday Cake" and the other is a new version of Chris Brown's, "Turn Up the Music (below)."



Both songs hit the Internet this week ... and both Rihanna and Brown have been pushing the songs on Twitter.

The songs seem to prove the rumors ... that Rihanna has forgiven Brown and is willing to move on. Earlier this week, Brown tweeted Rihanna "Happy Birthday" ... and Rihanna actually responded, "Thanks."

Rihanna is currently in London (see photo above) ... and Chris Brown was most recently seen in Miami.

As we previously reported, Brown is currently in a relationship with a woman named Karrueche Tran ... and we're told the two seem very happy together.

Lost in all the Chris Brown/Rihanna possible reunion madness is the fact that CB has a serious girlfriend -- and sources close to her tell TMZ the two of them are doing quite well in their relationship ... thank you very much! 

Sources close to Karrueche Tran tell TMZ she is unfazed by the recent rash of RiRi rumors. In fact, we're told CB and KT are now actually living together. 

As for CB showing up to Rihanna's birthday party, we're told that didn't bother Karrueche either ... because he came home to her that night and whisked her to Miami the next day to celebrate Valentine's Day.

According to our sources, Chris professes his love to Karrueche daily and he has no plans to leave her for Rihanna.

Almost makes you say, "Awwww" ... until you remember ...

Chris Brown and Rihanna are NOT back together, despite rampant rumors to the contrary ... Breezy's rep tells TMZ.

As we previously reported, Chris and Rihanna were spotted out at the same West Hollywood nightclub Sunday night. They left separately, but there was lots of speculation that the two had gotten back together.

But that's not true -- according to Chris' rep, the singer was with his actual girlfriend last night ... an aspiring model named Karrueche Tran ... not with Rihanna.

The rep adds, Chris and RiRi are just friends.