It's always hard to go from a friendship relationship to a physical relationship.
You say that you are new on the dating scene, well one thing of the first things you have to know about a relationship is always tell the truth. Just for future reference that is, because there is no point in doing it and it just causes more problems for both of you.
What you have to got to relise, is for someone to be comfortable around you, you have to be comfortable with yourself. Your worried when your around her that you should be making moves on her which makes you unsettled, and makes her uncomfortable. When your with her, be yourself because thats who she was friends with muck around with her tickle her or something i dont know. Sit with her with your arm around her, just something to make her feel less uncomfortable.
See when you dont kiss a girl, they think that you dont WANT to. Instead of looking like idiots, they go talk to your mates. Next time your with her, wait for the right moment and youll know when the right moment is and DO IT.
I'll be realistic here, if you dont do something she probably wont hang around and im sure you dont want that but also if you feel uncomfortable kissing her or anything, then dont do it because if your not ready then wait. Guys have to be ready to you know.