Asking out this girl while she's at work...?

So I've kind of fallen for this one beautiful girl who works at a Hollister (clothing store), but the past two times I've seen her there, I chickened out on asking for her number because I was just too nervous. I guess it's my fear of rejection and anxiety for what pressures I would have on me if she did in fact say yes and a relationship actually happened from that. But the main thing stopping me from fully talking to her is the fact that I have no idea if I would be putting her and her job at risk if I asked her out while she was on her shift, so I just don't do it, for the sake of being safe. I'm just wondering, do people do that? Do they ask girls out while they're at work? And if so, how do they do it smoothly? Thanks to anyone who helps out with this.