BOSTON — Cancer survivor Mary Shertenlieb wasn't about to let rain, wind or cold stop her.Shertenlieb crossed the Boston Marathon finish line at 12:18 a.m. Tuesday, about 13 hours after she started the race.The leukemia survivor was at mile 15 on Monday when she went to a medical tent, shivering, with purple lips, thinking she had hypothermia.She called her husband, Rich, and he suggested she come home, take a hot shower, put on dry clothes, then restart the run.The couple later went back to the spot she stopped and finished together, holding hands.