Spot said:
If I was in your shoes, i'd befriend all her co-workers so that they become your best supporters and encourage her to connect with you.
While you're working on that, find a reason to isolate her away from her co-workers so you can go for the number close and/or secure a date.
Spot's right. You should make her colleagues all adore you.
The problem with hitting on girls who are at work, is that it's their job to be nice to you. And if you approach one and tell her you want some spend some private time with her, there's no where for her to go if she doesn't like you.
There's a super sweet girl who I approached once at work because I couldn't handle the doubt "does she like me or not?!", so I just went in for it and she didn't appreciate it very much. It is her job to be nice after all, but damn, what does she expect?
My advice is that you should make your move, at least if you can't handle the doubt, but be subtle and be nice. Don't drive her into a corner