Rihanna's grandmother has died after losing her battle with cancer.

The devastated R&B star, who delayed a recent trip to Europe to spend time with her family and visit sick Clara 'Dolly' Braithwaite in hospital in New York, appears to have addressed breaking reports from Barbados, which suggest her grandmother has died, via Twitter.

As fans turned on the "Umbrella" singer following a shambolic performance at a Swedish music festival on Saturday, Rihanna had her late grandma on her mind, tweeting, "Goodbye grangranDOLLY get your beauty rest until I see you..." and then adding minutes later, "grangranDOLLY that is all."

And her ex-boyfriend Chris Brown's manager/mum Joyce Hawkins felt the singer's pain, offering her words of condolence after hearing the awful news.

Hawkins tweeted, "ANGEL MAY GOD BE WITH YOU AND YOUR FAMILY IN YOUR TIME OF SORROW. LOVE YOU ANGEL." The note prompted Rihanna to reply, "mombreezy thank you! Love u mama."

The "Umbrella" singer spent Father's Day in hospital visiting her sick grandmother, posting playful photos of herself with Braithwaite on Twitter.com and writing, "My heart smiled and cried all at once."

She admitted it was tough to leave her family as she jetted off to London the following day, tweeting, "I didn't wanna leave NY! I kept missing my flights."

The sad news might help to explain Rihanna's performance at Sweden's Peace & Love Festival, which left many Scandinavian fans upset and annoyed.

Local reports suggest the singer arrived onstage 45 minutes late and fans have taken to social network sites to suggest she appeared intoxicated.

One angry fan wrote, "Who the f**k allowed her on stage in this state?"

Another called her performance on Saturday night "disgusting and shameful."

Many fans walked out shortly after Rihanna began her set, after waiting for the headliner to hit the stage, and she upset fans who stayed by dedicating her version of Bob Marley's Redemption Song to Norway, even though she was performing in Sweden. She had performed in Oslo, Norway the night before.

Reports from Barbados suggest Braithwaite's body will be flown home to the islands from New York by air ambulance.