Kristen Stewart is reportedly "hurt" that her ex-boyfriend Robert Pattinson was dating her friend, model Dylan Penn.

An insider that knows Stewart said the On The Road actress is not upset that not only he dated a friend of hers just a few months after their May split but she's jealous because he took her to a concert. (Stewart and Pattinson regularly attended concerts during their four-year relationship.)

"When Kristen heard Rob had taken Dylan Penn out to listen to some music, she was not happy," a friend of Stewart's told Hollywood Life.

"She doesn't understand what's going on with Rob and his decision making. There are a million people Rob could date, but he picks someone like Dylan, someone Kristen knows," the friend explained. "Kristen is doing a lot better, but she still misses Rob and music was their thing, their bond."

Last week, it was first revealed that Stewart is reportedly "traumatized" by the news that her former on-and off-screen love moved on and began dating other women.

"She's traumatized by it," a source reportedly told OK! in the recent print edition, out on newsstands now.

Two eyewitnesses spotted Pattinson on dates with Penn and spoke to Life & Style Weekly about the sightings last week. The model, whose is the daughter of Hollywood actor Sean Penn and actress Robin Wright, was seen being affectionate with the British actor in public and at a private gathering in his home. An eyewitness saw the pair at Los Angeles' nightclub Viper Room on Sept. 7. The onlooker said they were "touchy-feely and very flirtatious," gave away several hints indicating that they have been dating for some time now. They were so comfortable with each other that it was obvious it wasn't their first date.

"There was a level of comfort there," said the eyewitness. "You could tell they've hung out a few times."

Their date didn't end there -- Pattinson later took Dylan to Chateau Marmont for drinks and French fries, added the insider. He had a car waiting for them to go club-hopping afterwards.

Another source told the publication they and a group of friends spent time at Pattinson's home in a previous occasion.

"They went into his kitchen, and he put his arms around her. Then he was kissing her neck and talking all lovey-dovey. It was clear they'd been out together before. When fellow guests left at 5 a.m., Dylan was still there," said the second eyewitness.

It was revealed on Thursday that Pattinson is currently dating anew brunette, his personal trainer Sydney Leibes. A friend of the petite brunette confirmed that she is indeed training him. The pair were photographed leaving the gym together.

An insider told RadarOnline that while Liebes might physically resemble Stewart, "she's not at all like her."

"She's down to earth, really energetic, uplifting, whereas Kristen is so somber and tomboyish. Sydney's a great match for Rob!" the source said.

Robert Pattinson & Sydney Liebes' Night Date PHOTOS Post-Kristen Stewart Split

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