By Dani Moritz-Long At 22 years old, eventer Jennie Brannigan was poised for Rolex and even the 2010 World Equestrian Games. She had the perfect partner in Cooper, a horse she had started as a 4-year-old, and an impressive track record — winning nine of 10 events in 2007–2008, landing atop the 2008 Adequan/USEA Gold