I'm too scared to tell her I like her?

So I met this girl about 5 months ago, and we've been talking for quite awhile, but only recently started hanging out. We're both smart, and have a lot in common (We're both 16 by the way). I just seem to be getting mixed signals from her, like for example; When I flirt with her, she usually flirts back, which is a good thing, but on the other end, sometimes she will tell me that we're best friends, when I'm clearly not her closest friend, which makes me think that she only wants to be friends. Lately we've been hanging out, just the two of us, taking walks and just sitting and talking and what not, but I really don't know what's going on. We don't hold hands or anything, because I don't think she knows that I like her as more then a friend. Also, I'm just too scared to tell her how I feel, I enjoy her company and I don't want to lose it, but I'd also like for there to be something more then friendship. Help?