What is the ruling of Islamic law on falling in love with a married woman, and what is the method of repentance from this sin and restoring the husband's right?

You did well to cut ties with the woman, and I praise Allah for your repentance and regret. Your addressing her with flirtatious words is a reprehensible act, and it becomes even more sinful given that she is married. What is incumbent upon you is sincere repentance. It appears that you are not obligated towards her husband except to supplicate for him and seek forgiveness for him.