How can I become closer with this girl?

So there is this girl I am friends with, and I really like her, she knows I like her too. I see her with other people and how close she can be with them and it makes me jealous. So what I want to know is how I can become better friends with her. We talk almost everyday, she used to tell me secrets but now it’s different. She tells me she cares about me, but I really want more. So how can I draw her closer to me?