Kristen Stewart 'can't compete for Robert'

Kristen Stewart is reportedly "devastated" as she realises she can't compete with Katy Perry for Robert Pattinson's affections.

Kristen and Robert dated for several years before splitting in May, apparently because he couldn't get over her affair with film director Rupert Sanders. He has since grown close to Katy, with the pair spending time together at music concerts and out of the limelight.

"[Kristen] knows Rob's met Katy's parents now, and seeing them on dates is really hard," an insider told Heat magazine. "She knows that when it comes to Rob's passion for music, she can't compare to Katy, so seeing them laughing away at a concert is devastating."

Earlier this month, Katy and Robert attended a Björk concert together. They did their best to keep things low-key, even arriving separately to divert attention. However, once inside they couldn't keep their burgeoning relationship under wraps.

"They were clearly into each other," a source explained. "They were standing very close together giggling into each other's ears - they barely stopped touching."

Kristen was apparently shocked when Robert called time on their romance. Even though he was quick to move his things out of the home they shared, she believed they would get back together.

Katy is also said to be mindful of everything the Twilight hunk has been through recently.

"At the moment, Katy's trying to keep things fun and light - hence the concert, rather than a romantic dinner," an insider explained.

"They're not at the boyfriend-girlfriend stage. They're just friends who have been attracted to each other for a while, are single and can finally do something about it."