i think you guys should just stay friends and see how things go as time goes on, because dating her could potentially hurt your friendship and from experience its really horrible to lose a friend and especially a best friend. if you continue to like her and if you realize its not just lust then you should tell her and see what she says.

"Actions speak louder than words"....I totally agree with that. Heres what you should do..Next time you see her walk right up to her and give her a kiss. See what happens. "Grow a sack" so to speak.

In my opinion, you're already in a relationship. You know everything about each other, talk to each other a lot, people see you and think you're together or think you should be together, and you both are attracted to each other. Not to mention that you care so much for her, you'd rather see her with someone she'd be happy with than to see her depressed in any way. Doesn't make sense that you two aren't together. It's obvious you both love the other and there's no point at all in staying apart. If you two can't be without the other, like you say will happen when one of you gets a boyfriend or girlfriend, then what are you two gonna do? Stay alone for the rest of your lives because you can't be friends and have someone else as a lover? No offense but that seems like a stupid reason to not be with each other.

It doesn't particularily mean it's love even though it may sound like it or feel like it at the time. I think it means you're infatuated or smitten with her.
Have you ever told her how you feel? If not, I think you should. She may feel the same way for you. You never know.