This is indeed a question that comes up often. It is important to remember that nonviolence does not mean inaction or passivity. There are many things you can do without resorting to violence.
But we have to start with ourselves, to see the causes of anger and hatred inside of us. Only when we rid ourselves of anger and develop compassion, can we see things with wisdom and take appropriate action in difficult situations. Maybe sometimes the effects are not immediately visible, but ultimately much more long-lasting.
She is still alive and president of the country now so she must have done something right.