Nicole Kidman ‘Believed She Could’ Save Marriage, Keith Urban ‘Hasn’t Been Honest’ (Exclusive Source)

Though Nicole Kidman was the one to file for divorce from husband Keith Urban, she wasn’t ready to throw in the towel on their marriage initially, according to a source.

The Oscar winner officially filed for divorce in Nashville on Tuesday, Sept. 30, citing irreconcilable differences. A family insider tells PEOPLE that “their split is turning dramatic,” as Kidman, 58, is “hurt and feels betrayed” by Urban, 57.

“Keith has not been honest,” the source continues. “She wanted to save their marriage and believed that she could, but it seems he’s already moved on.”

“It’s devastating to her. She’s shocked,” the insider adds.

Reps for Urban and Kidman did not respond to PEOPLE’s requests for comment.

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Urban and Kidman tied the knot on June 25, 2006. They share two children — daughters Sunday Rose, 17, and Faith Margaret, 14 — while Kidman is also mom to daughter Bella, 32, and son Connor, 30, from her first marriage to Tom Cruise.

A source in Urban’s circle told PEOPLE on Tuesday that the country star has “just been going through some stuff” as of late.

“He has been making questionable choices for some time now and this was not the case of them just drifting apart,” added a Kidman insider.

A source said in this week’s issue of PEOPLE, “Their lives were moving in different directions, and once he quietly set up his own place, it felt like the writing was on the wall.”

Kidman and Urban separated early this summer, and PEOPLE confirmed news of their split Monday, Sept. 29. The next day, the actress filed for divorce, though a third source said their breakup was a long time coming, at least according to the singer’s inner circle.

“For those around him, this has felt more like a gradual drift than some big shocking break,” the latter insider said.

This past summer, while Urban was on tour, Kidman and her daughters were “inseparable,” a source close to the family said in August.

They added, “Nicole lives full time in Nashville. She loves the tight-knit community and group of friends that she has built, and it’s the perfect place to raise her children.”