The singer apparently responded to a comment on one of her Instagram photographs with the insult, Sugarscape reports.
The picture, posted two weeks ago, shows Rihanna in a dressing gown, possibly smoking marijuana.
Rihanna captioned the image: "Friday night getting a lil fuzzy."
However, one Instagram user reportedly later posted a message suggesting that Rihanna was damaging her health, saying: "And she is going to end like Whitney [Houston] if she keep doing drugs like she's doing right now."
In her alleged reply, which has now been deleted but was screencapped by users, Rihanna said: "yea cuz Whitney overdosed on a joint!! F**k outta here u weak bitch!"
Rihanna caused controversy over the holidays when she uploaded an image online of herself with Chris Brown, who was convicted of assaulting her in 2009.
Rihanna's controversial outfits in pictures:
Copyright: Rex Features Broadimage/Rex Features