They have been living separate lives "for months now" pals told the Herald.
Vivienne went public for the first time that her five- year marriage was over at the TVNow Awards last month.
The Carlow beauty and her gym boss hubby Mark, who were together for over ten years, insist there is no third party involved.
The two are said to be doing their best to maintain a family life for the sake of their two children Ben (6) and Katie (4), with Vivienne staying at their luxurious home in Castleknock with the children while Mark has moved out.
They were reluctant to follow the lead of other high profile couples, including Grainne Seoige and Stephen Cullinane and Ronan and Yvonne Keating, by releasing a statement to announce their marriage break-up however.
Instead, friends claim that Vivienne took them aside on the night of the glitzy awards bash to discreetly share her news, knowing that it would eventually filter out.
The Compton model took centre stage at the Mansion House bash on May 22, when she was hired to walk winners and presenters on and off the stage during the show.
Vivienne (35) joined pals at the afterparty at Krystle but made her excuses and departed shortly after her arrival.
"The news that they have split up hasn't come as a huge surprise to anyone," said a close friend of Vivienne.
"They have been living separate lives for almost a year now and haven't been out together in months. Obviously, Vivienne is very upset, they both are. She's been to their holiday home in Portugal several times over the past 12 months with just the kids and she's planning to go there again this summer to get away from it all."
Vivienne and Mark married at a fairytale wedding in Ballintubber Abbey, Co Mayo, five years ago.
Last year, the glamorous beauty decided to pursue a new career as an actress and has been putting her all into making a name for herself on the stage since then.
Mark (36) has been heavily involved in helping to build his millionaire father Ben Dunne's fitness empire. The former Dunnes Stores Director currently has three gyms in Dublin.
Both Vivienne and Mark Dunne have declined to comment since news of their separation first broke yesterday.