What's wrong with her? Tell me?

So I have gone out with this lady twice, and we're going out again this coming Friday to see a show. I'm pretty sure that she knows I'm chasing her. She is sometimes nervous when talking to me in person. She and I are both busy. I always find an opportunity to chat with her online, but I don't do it on a daily basis because I don't want her to think that I'm needy or annoying. However, everytime I message her, she just gave me some plain replies and then left MSN. Also, she never initiates a chat with me online, it's always me who does it. When I see her in person, it's also me who initates a talk unless she sees me directly. I don't know what's wrong with her. We went out twice, and we had a good time. We got to know each other, and we even went to the formal party together as my partner.