"She's been talking about her upcoming wedding and how excited she is for it," an insider told the magazine.
Robin, 47, and 33-year-old Ben, — who is best known for his work in films X-Men: The Last Stand, Alpha Dog and Hostage — first met on the set of 2011 drama Rampart.
The couple were first linked romantically in early 2012 — a year and a half after Robin ended her tumultuous 20-year relationship with Sean Penn.
It will be Robin's third marriage. She was married to actor Dane Witherspoon from 1986 until 1988.
In 1989, she became involved with Sean following his divorce from Madonna. They wed seven years later after welcoming two children, Dylan and Hopper, now 22 and 20 respectively.
Sean and Robin initially filed for divorce in December 2007 but withdrew the petition four months later. In April 2009, the actor asked for a legal separation. He had a change of heart one month later.
The marriage finally came to an end in August of that same year when Robin filed for divorce. It became finalised on 22 July, 2010.
"It's like the high tide, low tide, right?" she said of the split in 2011. "You know it's going to happen daily — you're just not quite sure if the weather channel was accurate with the times.
"That's where the unknowingness flows in and you go, 'Okay, I have to relax and just give over to it.'"