This question cannot be answered due to the fact that girls are very complex and intricate in their thoughts and feelings. In your lifetime you may have figured out one girl, but fact is every single girl is different. So you cannot know how a girl's mindswork.
All i can say is that they mind's work based off of their emotions and feelings.
Read more: http://wiki.answers.com/Q/How_does_a_girl_mind_work#ixzz1dH2zO8QD
