My reply is to Orion34!
Sup? This is a girl replying to you! (How the heck did I find this forum??)
Men are visual creatures, this we all know. You can't base a woman's feelings for you just by her smile or body language. When you do that you choose to believe what you see instead of going by something she says to you. However, girls are tricky! We guard our feelings very well when we're crushing on somebody because mostly we feel vulnerable and don't want to appear weak or desperate. We're very, VERY conscious of how we appear and act around men, even around the ones we aren't interested in. I admire girls who can be so brave and just strike up a conversation with a guy they like.
Anyways, you said it yourself: She talks to other guys because she is a nice girl. How does she treat you compared to these guys? If it's similar then that tells you she's just being nice, especially because you guys work together she HAS to be nice to you! If she treats you extra special it might mean she thinks you're cute or sweet.
You catch her looking at you... when you're not looking? And when she's shopping? I have to admit that when I used to work retail and would come into the store when I wasn't working I would try to catch the eye of one of my fellow employees and wave if they saw me. Are you pretending you don't notice her when she's in the store? Because she could be trying to catch your attention to say hi because you're on friendly terms. It would be rude if she didn't! If you saw her looking at you I'd bet she would smile and wave and be on her merry shopping way. If you don't then she gives up and continues on her merry way anyway.
Body language and smiles can only get you so far. If you think you really like her then please, stop waiting for signs from HER and suck it up and be a man and talk to her since you have confirmed your feelings for her. Nothing is more irritating to girls than a guy who won't get off his butt and just talk to her, believe me! It's a huge turn off when a man won't be a man and acts like a coward when she is around. If she doesn't feel the same way then it'll be like a bandaid: it'll hurt at first but it'll be quick and you'll stop spending your nights thinking up ways of asking her out and the scenarios of you two together. Don't prolong this if it's on your mind so actively.
I wish you luck, buddy! Work relationships are like walking on eggshells, so think of what you could be risking... just don't think TOO hard