“To anyone who has seen [Alexandra] Ansanelli dance, it’s hard to imagine her as a civilian. Some dancers seem like regular people who just happen to have found themselves onstage. Others, like Ms. Ansanelli, appear to belong to a more rarefied universe. … [I]f she were to play a fictional ballerina, it would be a Vicki Baum-like character, ready to sacrifice everything for her art. But perhaps that’s exactly why Ms. Ansanelli is leaving ballet.”