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With a little help from her friends (and boyfriend), Ariana Grande kept the party going into the early hours of morning on Saturday.

After a 1 a.m. arrival at Las Vegas's 1OAK, the "Bang Bang" singer headed to her VIP table where her rumored boyfriend Big Sean and mother were waiting.

"She danced with her group for a second but then she quickly grabbed Sean, wrapped her arms around him and kissed him," an onlooker said. "At one point, she had her mom take a photo of two of them."

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Earlier, Grande performed at the iHeartRadio music festival, singing her hits and making a cameo during Nicky Minaj's set.

At night, though, she let loose, dancing and singing along to Big Sean as he rapped to many of the songs that DJ Que spun. Not to be outdone, Grande then grabbed the microphone to give an impromptu performance of her hits.

Although the singing couple hasn't formally announced they are a couple, Big Sean did refer to Grande as "my girl" in the microphone.

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"Give it up for Ariana Grande," he said. "She's looking good. She tore up that iHeartRadio tonight ... Y'all make some noise for my girl Ariana Grande. She looking good."

Later, Jason Derulo showed up to party with the couple.

"Ariana was having a great time," the source said. "She wore these black devil horns the whole night. She didn't stop dancing and she was fascinated by club's dancers. She was watching them, clearly impressed by their moves."