{blackbabes} Rihanna cuts fat for charity

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Rihanna is being accused of acting like a diva after she shot a charity public service announcement for UNICEF, but then caused costly re-editing delays after complaining that she looked heavier than usual in the online video clip.

The svelte songstress participated in UNICEF's Celebrity Tap campaign, which asks stars to donate bottles of their own tap water to raise money and awareness for impoverished children in need of clean drinking water globally.

Rihanna stars in a stylish black-and-white PSA on celebritytap.org, in which she slinks in a clinging black minidress down a hallway and into an ultramodern kitchen where she fills a clear glass with clean tap water and sexily drinks it.

A breathless voice-over says, "Water so hot, it can only come from Rihanna's faucet."

But sources familiar with the singer say that when she saw the original proposed video spot, she demanded it be edited because she thought she "looked heavy."

The pop star's self-involved demands caused "extensive delays," sources say, holding up the project's launch for more than a week at a cost of more than $15,000.

"We're surprised to hear that," a UNICEF representative told us. "She was not unhappy. We were very thankful. Rihanna was very collaborative and very participatory. What was shot was what exists now."

The rep added that tweaks are "part of the normal creative process" and "No reshoots were done." She said promotional work is done on a pro bono basis and any extra costs don't come out of the charity's coffers.

The Celebrity Tap campaign also includes celebrities Taylor Swift, Robin Williams, Adrian Grenier, Dwight Howard and Selena Gomez. Since 2007, it has raised nearly $2.5 million for water and sanitation programs for children in Belize, the Central African Republic, the Ivory Coast, Guatemala, Haiti, Iraq, Togo and Vietnam, according to the organization.

A rep for Rihanna declined to comment.