Robert moved out of the couple's Los Angeles apartment at the weekend after Kristen publicly apologised for cheating on him with her Snow White director Rupert Sanders.
Now Rob is nursing his broken heart at Reese Witherspoon's sprawling holiday ranch in rural California.
Reese, who is expecting baby number three (her first with new husband Jim Toth), co-starred with Rob in Water For Elephants last year.
A source told Radar Online, "As soon as she heard the news, Jodie contacted Kristen to offer her support.
"Jodie told Kristen to take no notice of the media bashing and said if she wanted to cry her heart out to her she's always available.
"Jodie loved Rob and is disappointed with Kristen for cheating on him. However, she knows at 22, she's still very young and unfortunately people make mistakes in life."
"Rob just isn't going to be able to get beyond the cheating one time or not," a source told People magazine.
Meanwhile, Rob is reaching out to Liberty Ross, the jilted wife of director Rupert Sanders.
"He needs to know for his own peace of mind if theirs was just a fleeting moment," a source tells the Daily Mirror. "He hopes Liberty can help him find the answers he so desperately craves."