What legal action can I take if neighbor’s mentally ill wife throws stones?

I have a neighbor who remarried, and his first wife is mentally ill. She throws stones, pebbles, etc., at our house. Once, she broke a window glass by throwing a stone. I am afraid that someday we might get seriously injured. We can’t even go to our terrace due to this fear, as she can throw anything at any time. We discussed this with our neighbor, but they haven't taken any action. Today, we had a serious fight. What can be done legally?