She certainly wasn't too tired and worn down to go to
war with fellow songstress Ciara via Twitter over the weekend, but hip-hop mogul Jay-Z is reportedly concerned that his protege Rihanna is overexerting herself at the expense of health.
The "Hard" star was diagnosed with bronchitis and laryngitis earlier this month, but still managed to perform at the Grammy and BRIT Awards. She's also been working hard to promote ...