"It's a thing that happens in any show," Rhimes said. "People love you, then there has to be a moment ... in which people disagree with where you're going creatively. But if you're telling your stories, well, they'll stick with you, hopefully, and watch us grow and change."
The series will get back to having fun next season, she said Thursday.
Rhimes acknowledged story lines that included death and infidelity represented a "darker journey," one that provoked some critics and fans. The series was hit by the real-life drama involving Isaiah Washington, who was fired after he twice used an anti-gay slur.
Rhimes said the show rose above that crisis.
"It was a difficult season for us behind the scenes. But creatively we moved in the direction we planned to move," Rhimes told a meeting of the Television Critics Association.
Washington moved on quickly, hired by NBC to appear in five episodes of the network's new fall drama "Bionic Woman." Last week, NBC executive Ben Silverman said he had spoken to Washington about coming to the network before the actor was dumped by ABC in June.
Rhimes, who had called Washington with the network's decision, was asked if she was aware he had talked to NBC and what her reaction was to his hiring.
"No, I wasn't aware of any conversation that happened before I had a conversation with him," she said. "I guess I don't have a reaction. He's a very talented actor. I hope he does really well with the `Bionic Woman.' I hope that show does well."
"Not as well as `Private Practice,'" she added, a reference to the "Grey's Anatomy" spinoff debuting this fall. The series stars Kate Walsh as her "Grey's" character Dr. Addison Shepherd and co-stars include Amy Brenneman, Tim Daly and Taye Diggs.