Rihanna Sued for Skipping Out on Grandma's $150K Funeral Bill

8:18 AM PT Rihanna's rep tells us the singer paid the bill in full, and the allegation that there's an outstanding balance is "completely false."

Rihanna sent her grandma out in grand style ... and now the funeral company has sent her a lawsuit.

Clara Brathwaite died in June, 2012. Her body was sent to Barbados for burial, and Rihanna wanted a party, complete with tents, multi-media large screens, huge exotic floral arrangements -- the whole kit and caboodle.

But parties/funerals come at a price ... and the company that threw grandma's final shindig claims the grand total was more than $150,000, and Rihanna paid only about a quarter of that and refused to pay more.

The lawsuit claims Rihanna claimed the bill was exorbitant and she refused to pay the balance. The funeral home claims Rihanna's demands came at a hefty price.

So far no comment from Rihanna's camp.