Brown has recently been seen with other girls, including his ex-girlfriend Karreuche Tran, who he previously split up with in order ot get back with Rihanna.
Rihanna hinted at the split on her Twitter, writing yesterday, "Never underestimate a man's ability to make you feel guilty for his mistakes."
Today she also wrote, "That "very rare" moment when ya wanna get blacked out drunk, but ya got an early morning!!! #ROCstarproblems."
Rihanna also posted a series of tweets over the weekend, which she later deleted. The 'Diamonds' singer tweeted, "Examine what you tolerate", "Goodbye muthaf**ker", "You give, you get, then you give it the f**k back" and "Claps for the basic b***ard".
However, she didn't delete a photo that she'd posted on Instagram, showing her snuggling up - with Chris Brown's arm visible in the shot.
Rihanna posted this snap with the caption 'Damn....... I miss my n***a'
Rihanna posted a picture of a letter to her fans, who she calls 'the Navy'.
The handwritten letter has a message of staying strong, with Rihanna writing, "There's no question that life throws us curve balls, we do our best to deal with them, take the lessons and keep it moving without regrets!"
She later adds, "Don't let one thing shake your core. Let our inspirations drive us, never steering from who we truly are..."
Rihanna finishes the letter, "We are all Unapologetic."
Listen to Rihanna and Chris Brown's 'Nobody's Business' duet below
Photos: Rihanna, Alicia Keys, Pink appear on German TV show