But will Robert Pattinson ever forgive her?
According to sources, Kristen Stewart seems confident that he will.
Insiders say the actress is 'pulling out all the stops' to win Robert Pattinson back, and is 'confident' that she can gain his trust.
'Kristen is pulling out all the stops with Rob, completely apologising and trying to make things right with him, but she is very confident that she is going to win his trust back,' one insider told RadarOnline.
But will her plan work?
'Kristen is doing everything in her power to keep Rob from breaking up with her. She knows how much he loves her and she really believes that she is going to keep him from dumping her,' the insider added.
'She wants to make it work. She’s trying to put this in the past and move on with her life with Rob.'
News that Kristen Stewart cheated on Robert Pattinson broke yesterday morning, when pictures surfaced in Us Weekly of Kristen in the arms of Snow White director Rupert Sanders.
As the shocking story raged on, Kristen Stewart fans accused the magazine of photoshopping the pictures, as they refused to acknowledge the news that could spell the end of Robert Pattinson and Kristen Stewart's relationship.
But by the end of the day, it became all to obvious the rumours were true, after the deeply private actress - who has yet to even acknowledge her romance with Rob - took the unprecedented step of admitting the affair, and making a public apology to Robert Pattinson.
'I'm deeply sorry for the hurt and embarrassment I've caused to those close to me and everyone this has affected,' she said. 'This momentary indiscretion has jeopardized the most important thing in my life, the person I love and respect the most, Rob. I love him, I love him, I’m so sorry.'
Snow White director Rupert Sanders later issued his own apology, stating: 'I am utterly distraught about the pain I have caused my family. My beautiful wife and heavenly children are all I have in this world. I love them with all my heart. I am praying that we can get through this together.'
While Kristen Stewart seems convinced she can win back Robert Pattinson after cheating, we're not so sure.
Either way, we don't think we'll be hearing from him any time soon.
Were you surprised by the revelations that Kristen Stewart cheated on Robert Pattinson? Do you think Rob will ever forgive her? Let us know in the comments box below…