How can I [19 M] gauge if [17 F] likes me?

So I work part-time in an office for a department store. Once a week, I work with a girl who I really like. I want to ask her out, but I have no idea if she likes me back or not. I don't want to just plain ask her out because I sit straight opposite her in a tiny room and I don't think I could deal with the awkwardness if she said no. We're not allowed to leave the room while we're working, so there would be no avoiding her.

So how can I get a better idea if she likes me without risking too much awkwardness?

tl;dr: Really like the girl I work with. Looking for a way to see if she likes me without asking her out straight.