"She's doing the best she can and taking it day by day," a source tells PEOPLE of Lambert

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After 10 years together, country superstars Blake Shelton and Miranda Lambert are calling it quits. Subscribe now for an inside look into their shocking split, only in PEOPLE.

As Miranda Lambert‘s fans continue to express shock that her marriage to Blake Shelton has ended, the singer is staying focused on putting one foot in front of the other.

“She’s doing the best she can and taking it day by day,” a source tells PEOPLE of Lambert, who fell for Shelton after dueting with him for a concert special in 2005.

Rumors of trouble in their marriage had dogged Shelton, 39, and Lambert, 31, since their 2011 wedding, but the source says the finalization of their divorce has left Lambert “sad and trying to process everything.”

“This is not the future we envisioned,” the pair said in a statement to the Associated Press on Monday. “And it is with heavy hearts that we move forward separately. We are real people, with real lives, with real families, friends and colleagues. Therefore, we kindly ask for privacy and compassion concerning this very personal matter.”

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