A source tells ET the 34-year-old fashion designer is "doing really well," and that going back to work has been "keeping her distracted."
Mary-Kate is really proud of the work that she and her twin sister, Ashley Olsen, have done with The Row, the source says, adding that she has enjoyed diving back into it. The source notes that although Mary-Kate has been staying in the Hamptons, she has also been coming back into New York City to work out of her Manhattan office.
As for why Mary-Kate and Ashley still continue to work given their wealth, a question fans often wonder, the source says it's because they've "never liked being idle."
"Mary-Kate has so much to offer and has a great work ethic," the source says. "It's not about the money. It's about the personal satisfaction."
ET reported back in May that Mary-Kate filed for divorce from Olivier in New York after the state lifted its moratorium on nonessential and nonemergency court filings. The two married in November 2015 after three years of dating.
A second source told ET at the time that Mary-Kate and Olivier were simply at different places in their lives. "Olivier was very attracted to Mary-Kate's ambition and success," the source said. "He very much respects her work ethic and is beyond proud of everything she has ever accomplished."
"Her career is a big part of who she is, and he never would want to change who she is," the source added. "He has worked incredibly hard his whole career and is now at a point where he wants to slow down and enjoy his life."