How can I tell if she likes me?

wow dude, you are way over-analyzing this thing! don't thinks o deep about it, ask her out or send her a note or letter, friend online, do something. you will never know unless you talk to her. I am an adult now, but I find out all the time that guys liked me back in high school, and they never told me. Some of them I probably would have dated, if they had told me. The worst that can happen is she will tell you 'no'. But nothing will ever happen if you don't talk to her at all. It doesn't sound like you've blown it yet, so go for it.