“When the painter Susan Rothenberg moved to New Mexico from New York City in 1990 at the age of 45, she didn’t give a lot of thought to the parallels between herself and Georgia O’Keeffe, another woman who gained fame in New York and began spending a lot of time here at around the same age.” But with a retrospective of Rothenberg’s work now showing in the Georgia O’Keeffe Museum in Santa Fe, “the comparison has become hard to avoid.”