Charlize Theron is "fuming" over Kristen Stewart's affair with director Rupert Sanders.
The Oscar-winning actress is reportedly outraged that her Snow White and the Huntsman co-star cheated on Robert Pattinson because she is close friends with the 41-year-old filmmaker's wife, Liberty Ross.
A source close to Charlize told RadarOnline.com: "Charlize is absolutely fuming with Kristen for having an affair with Rupert.
"She is very tight with Liberty, has often socialised with the family over dinner and cannot believe Kristen has done this.
"When they were all filming Snow White and the Huntsman, Charlize felt like an older sister to Kristen, and they were always sharing advice."
The 36-year-old South African beauty became so close with Kristen (22) that she asked the 'Twilight' actress to be her adopted son Jackson's godmother, and now feels betrayed and confused about how to handle the situation.
The insider added: "Charlize confided to her new pal about her adoption plans. She even asked Kristen if she wanted to be her baby Jackson's godmother - that was how close they were.
"But Charlize had no idea what was going on between Rupert and Kristen and now feels completely betrayed by the whole incident.
"It's certainly left Charlize between a rock and a hard place, because she feels great sympathy for Liberty and the kids and yet, she has a sisterly love for Kristen."
Kristen was caught on camera locking lips with Rupert on 17 July, but has branded the incident a "momentary indiscretion" and issued a formal apology to her boyfriend of three years Robert.
The statement read: "This momentary indiscretion has jeopardised 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."