The Devil Wears Prada actress Anne Hathaway put on a brave face at her latest film premiere last night after breaking up with long-term boyfriend Raffaello Follieri, the Mail Online can reveal.

The 25-year-old movie star ended her four year relationship with Italian-American businessman, 29, over the weekend.

The Brokeback Mountain star's decision follows over a year of scandal linked to Follieri.

Last week, it was reported his charity Follieri Foundation, which funded vaccination programmes in developing countries, was being investigated by the New York State Attorney General's Office.

Hiding her heartbreak: Anne Hathaway was all smiles at the Los Angeles premiere of her new movie Get Smart last night

An insider tells the Mail Online that Hathaway made the painful decision to end their relationship because of the effects his controversial business dealings could have on her career.

Hathaway served as a director on the charity's board until some time last year, with her rep saying: 'Since she is no longer associated with the foundation, why would you expect her to be familiar with all of this,' when asked about the investigation.

A source said: 'It's heartbreaking for her to dump him, and she's devastated that it's come to this, but she really didn't have a choice. His scandals were hurting her reputation.'

Despite their split, it remains to be seen if the separation is permanent.

The couple were reported to have split briefly this year after Follieri was sued by a former business associate for bouncing a  $215,000 cheque.

Criminal charges against Follieri were dropped after he turned himself into police and  settled the outstanding bill.

Kaput: Anne Hathaway has ended her four year romance with Raffaello Follieri

Follieri often visited Hathaway on the Boston set of her upcoming movie Bride Wars, but they were regularly spotted arguing by crew members.

A friend said: 'They fought so much while Anne was making the movie, she genuinely started to wonder if the relationship was worth all the pain.'

Hathaway also heard rumours from her friends in New York that the businessman had been flirting with other women while she was away filming.

The friend added: 'Raffaello would only ever visit her on sets for short periods of time.

'He was very caught up in his social life and making connections in New York, and stories would get back to Anne about his late nights and carousing, usually with models in the immediate vicinity.'

During the making of Get Smart last summer, Hathaway formed a friendship with co-star Steve Carell, who lent her a supportive ear during her problems with Follieri.

Hathaway's split from Follieri may mean she finally moves to Hollywood, after years of insisting she would remain on the east coast to stay close to her beau.

A pal said: 'She seemed to really be enjoying her freedom, and making new friends in L.A., especially Steve.

'Anne really wants to find a guy like Steve, and if he weren't married, I have no doubt she would date him in a second.

'She's such a fan of his work she couldn't help but quote episodes of 'The Office' to him when they first met. She thinks he's amazing.

'Even though she loves being near her family, a move to Los Angeles could mean better roles, more money, and a better pool of potential boyfriends.'

Support: Anne Hathaway and her Get Smart co-star Steve Carell