Ariana Grande a 'nightmare' during SUTC fundraiser

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Ariana Grande a 'nightmare' during SUTC fundraiser

Ariana Grande was allegedly a "nightmare" during the Stand Up To Cancer fundraiser last night (09.05.14).

The 21-year-old singer took to the stage at the annual event yesterday and an insider claims she was difficult to work with because of her diva antics backstage.

A source told the Daily Star newspaper: "Ariana was a total nightmare. At first, it was her warning the lighting crew if they used red spotlights she would go berserk.

"But then she kept everyone waiting while other stars came in and did their thing.

"We've been on set with Lady Gaga, Madonna and Mariah [Carey], but combined they aren't as rude as she was. When she caught one poor guy grimacing, she barked, 'Who the f*** do you think you're looking at?' "

The insider added: "The whole episode was kind of surreal because once Ariana had calmed down, she was all sweetness and light. But it wasn't long before she stormed off again, unhappy with her outfit."

The brunette beauty, who lost her grandfather to cancer recently, gave an emotional performance of the title track from her new album 'My Everything'.

Taking to Twitter after the show, she tweeted: "sobbed my eyes out as soon as I got back. idk how he was just here & now he's not & I'm singing a song in his honor. sucks a lot #f*ckcancer (sic)."