We both know we've fallen for each other, but she has a boyfriend....what do I do?

You are fast walking directly in to 'heartbreak'. My advice to you would be that, if you want to have a relationship with this girl beyond work [which i think is a bad idea] You will need to inform her directly, at which point she will have to make a decision weather to end her current relationship, or just maintain a simple friendship with you. Beyond that, you don't do anything, for moral and ethical reasons. If she truly wants to have a relationship with you, then she will end her current relationship with little hesitation. If not...doesn't look like it was meant to be. I don't want to sound like a cynic, but the whole thing really isn't fair to you, her or her current BF. Best of luck!