KRISTEN STEWART had a gay time OUT without ROB PATTINSON with hot new gal pal.

While Rob Pattinson is far away filming in Australia, his on-again, off-again girlfriend Kristen Stewart is stepping out with a hot new pal – Katy Perry’s assistant Tamra Natisin. And that could spell big trouble for the screen hunk and his “Twi­light” co-star, who are still picking up the pieces after her shocking affair with her married “Snow White and the Huntsman” director Rupert Sanders, 42.

“Rob will hit the roof when he sees photos of Kristen and Tamra hanging out together,” predicted an insider. “It’s obvious to all of her friends that there’s a romance brewing between them.”

On March 3, free-spirited Kristen, 22, raised eyebrows by lavishing attention on Tamra at Hollywood’s Hotel Cafe. “They arrived together and spent the entire night talk­ing to each other, ignoring everyone around them,” revealed the insider. “Af­ter a few hours, they left together. Lately, Kristen and Tamra have been spending all their free time together.”

Meanwhile, 26-year-old Pattinson has reportedly banned Kristen from visiting him so he can concentrate on his film project.

But sources say she doesn’t seem to be missing him now that she’s found Tamra, who’s said to be very vocal about equality for same-sex couples and even attended a gay pride rally in the past year.

Now, people are wondering if Kristen could be following in the foot­steps of her mom Jules, a writer/director who moved in with her girlfriend after splitting from her husband in June 2010, according to the source.

 “All of Jules’ close friends are gay,” said the source, “and she’s made Kristen more comfort­able with exploring her own sexuality.”