I have asked a couple of my female friends about this.
She seems to be one of the 'out of sight, out of mind' types. It didn't sound to me like she was intentionally giving you mixed signals - it sounded more like she was just doing whatever came next. The impression I got from you is that she isn't the kind of person that would intentionally hurt another person's feelings. So...you're in the apartment, she takes a nap with you. She's dancing with some guy, she kisses him. I don't know that these actions reflect how she really feels - sounds like she's running on autopilot.
So... if you want to be involved with this one (and it does sound like you like her), spend as much time as possible right in front of her face (or taking naps). Call every day. ask her to do stuff all the time. I mean, it's a fine line between trying to be visible and being a pain in the ass, but I think it's worth a shot.
I think all of us have our weird-ass personalities - this one is just apparent right away, instead of in six months. My bet is that once she has some EMOTION invested in a relationship, the out of sight out of mind business will not be as important.
Another friend thought it might be possible she is polyamorous. That seems to be a big thing in the crowd that frequents the Mercury. I don't really get that impression from her, but you never know. I am not so sure how to approach the situation if that is the case though. I know for certain I am not interested in a polyamorous relationship. It's just not my thing. I can deal with a slow moving and casual relationship, but knowing I am one of many and having that in front of me all the time would just be too difficult.