Well it can't hurt to at least try and ask her to go with you. I mean.....its not like a date.....its more like going to something that both interests you guys. Give it a shot. If shes not into you like that....then u will probably find that out when you hang out together... and the nice thing will be that it won't be an actual date.....but just hanging out. If anything you will have her friendship. And you can always play it off like all you ever wanted was just to be friends with her.......if she isnt interested in you like that.

I definately see this as a win-win situation.

if her sister isn't there/or

2- Find her number in the company phone book and call her myself. I'm thinking this option has a little stalker feel to it...