She may be prude or she just may not like you. Some girls just do not like to be touched. They like to keep a strong sense of personal space around them. This is look, talk and smile but do not...
Be confident! Play it safe, start off slow, and don't pull any crazy moves. To start it off, watch a movie and cuddle. Start talking to her and when she looks up at you kiss her. Then go from there....
Because girls are not boys, or to put it scientifically, for the human reproductive system to work you need both male and female. If girls weren't girls the human race would die out.