|Robert Pattinson on the Daily Show|
She is also hoping that eventually the two can work on building a friendship.
An insider said: "Just like his devout fans, Kristen tuned into Robert's interview with Jon Stewart with drawn breath.
"But after seeing him deflect the questions about her, Kristen's anxiety soon disappeared and instead she was filled with regret."
Apparently she was hoping she would get a second try at their partnership but seeing him helped her realise it was over between them.
The source continued to website RadarOnline: "While she was obviously relieved that Robert didn't trash her, the realisation that their relationship was finally over hit her hard.
"Kristen was praying that after the dust settled she would get another chance and she was clinging on to that hope. But she knows now that it's not to be.
"Instead, she's believes that they can now work on a friendship and is desperate to apologise to Robert in person for her affair with Rupert."
Robert refused to be drawn on the subject of Kristen cheating on him with married 'Snow White and the Huntsman' director Rupert Sanders during his interview on Monday night .
Despite the host's probing efforts to get the 26-year-old actor to talk, Robert laughed off Jon's attempts and quickly moved on to promoting his new movie 'Cosmopolis'.