The fashion mogul filed for divorce from her French husband after four and a half years of marriage

Mary-Kate Olsen, 33, has been working since before she could walk or talk. The fashion mogul and her twin sister, Ashley, famously played Michelle Tanner on Full House when they were just babies and have continued working ever since ⁠— from launching their own production company to now running a fashion empire.

But according to a source, Olsen's focus on her career caused tension in her marriage to banker Olivier Sarkozy, 51.

"Mary-Kate is extremely hard working and focused on her business. Her work schedule is beyond disciplined," a source tells PEOPLE in this week's issue. "She is the type of person who would never complain about a 12 hour work day. Olivier never understood her drive and passion. He would have loved to have a stay-at-home wife."

Mary Kate Olsen, Olivier Sarkozy
Mary-Kate Olsen, Olivier Sarkozy
| Credit: James Devaney/WireImage

For more on Mary-Kate Olsen, pick up this week's issue of PEOPLE on newsstands now. 

On April 17, Olsen privately signed papers seeking a divorce from Sarkozy, but because of the coronavirus crisis, New York City courts haven’t been accepting divorce filings except in cases of emergency. On May 13, Olsen requested an emergency order to file for divorce, citing fears of being forced out of their apartment. Her request was later denied by a judge.

The source adds that Olsen, who runs two successful clothing brands, The Row and Elizabeth and James with sister Ashley, rarely takes a vacation.

"Olivier loves traveling to tropical places with his French friends," says the source. "He traveled without her several times."

Mary-Kate and Ashley Olsen
| Credit: Kevin Mazur/WireImage

Last year, it was reported that their clothing brand The Row has sales of between $100 million and $200 million a year, while their other brand Elizabeth and James rakes in $89 million. The sisters have also won five prestigious CFDA awards including the 2019 award for Accessory Designer of the Year.

Adds a fashion insider: "Mary-Kate is super career focused and he wanted her to be more available. But you can't control a girl who has been on the billionaire track since her 20s."

* With reporting by Pernilla Cedenheim