if she never told you then you have to hear it from her.
you are in a difficult position because you have to wager the friendship loss risk factor.
DONT get drunk and tell her, good idea in the way you could be like "hehe i was drunk" if you get shot down, but however its not cool
do things alone with her away from work or skool and mutal friends
then when its right, tell her.
if you dont want to lose her friendship, make a strong bond with her so that if she does shoot you down your friendship will be able to continue.
*kat. <-- lady i just like i wont get you outta my mind i feel love for the first time and i know that its true i can tell by the look in your eyes