Is Ariana Grande and out of control diva? That’s what some people are saying, according to the Daily Star. The newspaper quotes a source as saying the singer was a “total nightmare” during the ‘Stand Up To Cancer’ benefit concert that took place over the weekend. But before you write her off as just another pop star with an oversize ego, the report might not be entirely accurate. Gossip Cop disputes the claims, citing their own source, who called the singer “fantastic” to work with.

According to the source who spoke with the Daily Star, Grande’s diva antics began with her “warning the lighting crew if they used red spotlights she would go berserk.” The source goes on to say that the singer “kept everyone waiting while other stars came and did their thing,” and that “We’ve worked with Lady Gaga, Madonna and Mariah [Carey], but combined they aren’t as rude as she was.”

The source remarks that “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.”

Gossip Cop’s source, meanwhile, says that “There’s nothing true about any of it,” adding that “[Ariana] was fantastic…No one had a problem with her and vice versa.”

Whatever the truth may be, the one thing we know is that Grande had a very personal reason for participating in the concert. The pop star recently lost her own grandfather to cancer. After giving an emotional performance of her new song “My Everything,” she took to Twitter, writing: “Sobbed my eyes out as soon as I got back. idk he was just here & now he’s not & I’m singing a song in his honor. sucks a lot #f*ckcancer.”