Stood up

So, there's this girl that started working at my company like 6-7 months ago. She's on a different floor but we have to deal with each other once a week for about 10 mins.

We're both shy (not very shy, just the "not chatty with strangers" or "blushing occasionally" type) so we weren't talking too much at first. After we got comfortable with each other we were talking a bit more, then a few months ago I became attracted to her and I started to flirt a little. I can't say if she was flirting back or if she was trying and failing b/c I'm not that perceptive to this, unless the other person is really obvious. All I can say is that she was always smiling, laughing at my jokes, asking what's written on my t-shirt, etc

Then we didn't meet for 3-4 weeks until last Friday, we didn't get to talk a lot b/c it was right before the end of the shift, but we bumped into each other into the street, she was going to take the train home, I offered her a ride, she said she doesn't want to inconvenience me, then I found out she is living close to where I was going (true story) and she said ok. In the car she was very chatty, we ended up talking about movies and I asked her if she saw some movie (romantic comedy)

She (with big eyes): No
Me: Do you know the movie?
She: uhhh... no
Me: Let's go
She: When?
Me: I don't know, now?
She: How about tomorrow, right now I 'm tired; we can go in the afternoon or in the evening, whenever you want

We exchanged numbers and I called her the next day, she didn't answer, called her again after an hour and something and left her a vm with my phone, but nothing. So I have two questions:

1. What the hell just happened? She seems too nice to act this douchy, If she didn't want to go out she could have invented something on the spot or call me the next day with something. Or answer my call and tell me she can't go b/c blah, blah. I mean I wasn't some random guy that she'll never see again. Which brings me to my second question:

2. How do I proceed going forward? We have to meet today at work, we were actually supposed to meet Tuesday, but I kept pushing back. Do I act like nothing happened, do I give her the cold shoulder, do I ask her WTF? (well, not exactly like that)

Thanks