The girl approached you and now she is withdrawing yourself. When you become too “nice” and get upset with her every mood swing, your value decreases. Is she becoming “cold”? So you become “ice cold”. When you ask her questions or pick her up, she feels like you are in her pocket. Give her some space so she can realize what life is like without you.
AskApril is right that to give her flowers, invite her out, flirt with her and compliment her. If despite all these efforts she does not give a positive response, then understand that you two are not a match and move on.