Girls or ladies are very sensitive and emotional.
They really need that someone should care for them.
If you really want to show love to her, make here feel like you really care, Spending some time with her, sharing some beautiful and cherishing moments, fulfilling her desires are the everlasting tricks to make a girl happy.
Appreciating the little things that he or she does for you, occasional kisses and holding hands, telling her she looks beautiful now and then, especially when she has taken efforts to look her best on occasions, most importantly buying gifts as surprise does the trick!! :)
one of the way may be gifting her regularly and taking her to movies and candle light dinner. fulfilling her wishes and keeping her happy may be one of the way.