People describe Erika Halweil, a longtime yoga teacher in the Hamptons, as someone who has a lot of backbone in every way. She has great posture. She rarely gets upset over things like parking tickets or bad-hair days. (Naturally pretty, she probably doesn’t have many.) She is sometimes stern but never shy.

“Erika is exuberant and totally at ease with her exuberance,” Brian Halweil, her brother, wrote in an e-mail. “If I were to bump into a celebrity at a party, I would probably clam up and try to think of something interesting to say. Erika would greet the person with a huge smile and loud hello and probably hug them.”

Ms. Halweil, 36, grew up in New York in a tightknit family of four who loved to spend weekends together foraging for elderberries in Central Park, watching old Laurel and Hardy movies or surf-casting on Long Island. She always hoped she would replicate that kind of happy family unit in her own life. Instead, in 2008, she found herself living in Sag Harbor, N.Y., with a young daughter, Milla, an unhappy marriage and a huge mortgage she and her husband could not afford. “Broken marriage, broken house,” she said.

While her marriage —and also her yoga practice — were foundering, she began regularly running into Corey De Rosa, an intense, thoughtful yoga teacher in Sag Harbor. “I was bumping into him three or four times a week, randomly, outside the post office, on a bench on Main Street,” she said. “He was so inspired and I was pathless.”