Why can't I be mad with someone who I like?

Well, I bumped into her earlier today and we both said Hi back to each other. I asked her if she had any plans for the weekend and she mentioned not that much at all. I told her the same. Then I told her that I'm in a weird situation right now that I'm in and I don't know how to solve it. Then she basically (get this),'If you need anything, let me know and I said, 'I will, as we both parted ways to get back to work. In a general consensus, I basically lied to her about what I previously mentioned to her before hand. It was about her and I couldn't tell her because we both work at the same place. After all that, I started to laugh because of the fact, that I told myself that I didn't want anything to do with her. I didn't want to talk to her, See her, or even come into contact with her, and yet here I am, I did.