Pattinson split from Stewart last month after it was revealed that she cheated on him with her 'Snow White and the Huntsman' director Rupert Sanders.
It was Pattinson's first public appearance on the show since then. "Just like his devout fans, Kristen tuned into Robert's interview with Jon Stewart with drawn breath," femalefirst.co.uk quoted a source as saying.
"But after seeing him deflect the questions about her, Kristen's anxiety soon disappeared and instead she was filled with regret," added the source. Apparently she was hoping she would get a second try at their partnership but seeing him helped her realise it was over between them.
"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," said the source