Alfonso Signorini - a close friend of the Italian actress - was shocked by the break up, as George appeared to be doting over her when he saw her just last week.
He told Italian TV show Rai Uno: "It's all over. It has come as a real surprise to me. They were getting on really well.
"From what I know it was him who dumped her and she stormed out of the villa. I've tried to get her on the telephone but it's switched off."
Describing his recent day with the 32-year-old model, he added: "She must have had about 60 text messages from George! She was so excited about meeting him as he had a few days off from shooting his film."
George, 50, has been making 'Gravity' â which also stars Sandra Bullock - in London before flying over to his Lake Como estate where he broke the bad news to his girlfriend of two years earlier this week.
Alfonso added while he believes the couple's relationship was genuine, it was "complicated".
He said: "I can tell you it was all For Real. They were deeply affectionate towards each other."
"George is actually very fatherly but at the same time they did have a very complicated relationship - It's not easy to be with a star of that status."
Earlier this week, the couple issued a joint statement saying: "We are not together anymore. It's very difficult and very personal and we hope everyone can respect our privacy."