She is obviously the indecisive type, so I don't think making her jealous at work with the other girl is a good idea - she's bound to think that you're an item; and then she definitely won't make the effort to meet up for fear of embarrassment, rejection and humiliation.
Just ask her to be totally straight with you - pin her down (in the metaphorical sense of course!) and just say 'Look, I like you, you say you like me. Please can we either set a date to go out here and now, or shall we just leave it - because this is just going round in circles. I'd much rather you just say if you're not that interested - don't worry about offending me, I'm a pretty resilient guy'.
I definitely, 100%, totally would recommend that you DON'T try and make her jealous!