Actress Valerie Harper was taken to the hospital Wednesday just before her evening performance in “Nice Work If You Can Get It” at the Ogunquit Playhouse. The star, who has been playing the role of Millicent Winter alongside Sally Struthers, remained hospitalized Thursday morning but was “resting comfortably,” according to a press release emailed by Cheryl Farley, the theater’s marketing director. Harper “will remain in the hospital for observation for the time being,” the release said. The star, who played Rhoda Morgenstern in “The Mary Tyler Moore Show,” was diagnosed with lung and brain cancer in recent years.