A source tells Radar Online that K-Stew was "relieved" Rob didn't air their dirty laundry during his Daily Show appearance, but seeing him deflect questions about their relationship made her realise she's never going to win him back.
"While she was obviously relieved that Robert didn't trash her, the realisation that their relationship was finally over hit her hard," said the source.
"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."
Rob and Kristen split three weeks ago after Kristen was caught in an affair with her Snow White director Rupert Sanders.