(Cover) - EN Showbiz - Rihanna reportedly had a challenging time making it through her Brit Awards rehearsals after partying the night before.

The Barbadian singer turned 24 yesterday and had to spend some time going through the choreography for the annual music show.

But an insider told Mail Online that she was tardy for the scheduled appointment and looked like she wasn't that happy being there.

"Rihanna turned up to rehearsals really, really late," the source alleged.

"She didn't do any singing or dancing whatsoever. She literally stood on the stage like a zombie.

"She made all of her dancers, about 50 of them, dance around her and she stood looking really pi*sed off like she'd been dug up."

Rihanna tweeted to her fans that she was feeling a little sorry for herself.

"I can't believe I'm pullin an all nighter on my BDAY (sic)!!!" she wrote.

The Umbrella star had apparently been out partying the night before as an early birthday celebration. (C) Cover Media