Ariana Grande and Big Sean split? Nickelodeon star responds to break-up reports on Instagram

Nickelodeon star Ariana Grande has denied rumours that she split with boyfriend Big Sean.

Star magazine had claimed that the couple called it quits after Christmas.

"During the last visit they had together, right before Christmas, Ariana reached for Sean's phone and he about jumped out of his seat," an alleged source told the website. "She questioned why he was so jumpy, and insisted on seeing his phone."

"He tried to play it off and swears he hasn't hooked up with anyone since they became official, but Ariana was devastated," the insider added. "She couldn't believe the sort of things she saw them talking about to him!"

The Problems singer allegedly found explicit images on the 26-year-old rapper's phone.

"She refuses to return his calls. She feels completely violated and has lost all trust in him," the source went on. "His grandma passed away a few days later and she hasn't even called to check up on him. They're done!"

Grande, who previously dated Australian star Jai Brooks and The Wanted's band member Nathan Sykes, posted photos with Big Sean on Instagram, silencing the break-up reports.

Big Sean and Grande had confirmed their relationship in August after they were pictured holding hands backstage at the 27th annual MTV Video Music Awards.