The troubled actress -- who was arrested in New York City on May 23 for allegedly possessing marijuana and throwing a bong out the window of her high-rise building -- went off on the singer on Sunday, May 26, in a series of tweets that she quickly deleted, reports TMZ.
Bynes, 27, shockingly tweeted "@rihanna Chris Brown beat you because you're not pretty enough."
She then quickly deleted the insult before posting another rude message to Riri, 25, before deleting that one too.
According to TMZ, it read: "@rihanna no one wants to be your lover so you call everyone and their mother that I almost named my new dog Rihanna."
Rihanna's pointed response? "Ya see what happens when they cancel Intervention?"
But Bynes was intent on having the last word, tweeting -- then deleting -- one final barb: "@rihanna unlike ur fugly faced self I don't do drugs! U need the intervention dog! I met ur ugly face in person! U aren't pretty u know it!"
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