WASHINGTON — She was the face of mass protest, but long ago lost her faith in protesting. Then, last year, hundreds of thousands of women set out to march on Washington, and Jan Rose Kasmir knew she had to join them. “When Trump was elected president, I couldn’t not participate. … It seemed like the only way to get my voice out there,” said Kasmir, 68, who was 17 when a photographer snapped a now-iconic image of her offering a chrysanthemum to National Guardsmen during a 1967 protest against the Vietnam War. Kasmir gave up protesting when public opposition failed to stop the Iraq War in 2003.