Regarding this question, Dr. `Abdul-Fattah `Ashoor said,
Allah the Almighty enjoined the believing men and women to lower their gaze and observe modesty. Marriage is the only legitimate avenue for men and women to exchange love and feel affection.
So, if a man sees a well mannered lady and he fell in love with her and the lady also loves him, the man should goes to her father to establish a legitimate marital relation. The lady can also seek all the means to to establish this marital relation.