Well you'll never know unless you make a move
and an advice from me would be: make a move quickly (ask her out, or do something else if you've got some great idea)... if she likes you, there you go...
if not, well you now know it early enough to re-see her just as a friend...
the more time you take to know what she feels about this whole thing, the more you get attached, the harder it is to back out :s I've had bad experience with that