Please tell me what this girl's behaviour means and how should I act. Here's the story:

I met this girl in a bar about a month ago. She is two years older than me (27 while me being 25), qute and smart. She is also strong and confident which I find very attractive. Two days after we met I called her twice to ask her out on a date but she didn't answer her phone. Then I texted her with no response as well. I thought that after sobering up she just decided she wasn't actually interested in seeing me again which I am able to live with (happened before). But the next day she calls me and we set up a meeting. To be fair I found the atmosphere during the meeting a bit stiff but that's usually the case on a first date. Nevertheless, I decided to give it another chance and called her after some time. Again, she didn't answer her phone and I got a bit upset to be honest because I didn't expect to be rejected (the other way round if anything). And then - you guessed it - the next day she calls me back and we set up a second date. This time I had much more fun and it surprised me how sharp she was. She seemed to be much more relaxed in my presence than before and to have fun as well. For the next week I was out on a business trip (which she new about) and we weren't in touch at all. Yesterday I got back and today I tried to call her and as you can imagine she didn't answer her phone. What does mean? Do you thing she could be doing this on purpose to show her dominance? Or maybe she's just not interrested in me? The result of her attitude was that the both times we met she was the one picking a day and time. She tells me she's very busy and has many friends she doesn't want to neglect and also that she is looking for a new flat and a roommate so she has to see many people. I also know she has a successfull career. But still it looks a bit suspicious to me. How busy can you be to not answer someone's calls for three times in a row? She never sent me a 'thank you for the evening' text, never called me to see how I was. At this point I am really interested in seeing her again but I've already learned that being to intrusive is the best way to screw things up so I decided to do nothing until she calls me back (if she does that at all). So guys, please help me because I suck big time at understanding women.