Pretty tough question to answer, but...?

Well there is a girl that is always so quiet to me, let me rephrase that. We are both so quiet when we talk together. I thought it was because she hated me but I asked her that and she said no. So then I told her that I don't understand why we are so quiet when we talk together. She just smiled and giggled a little bit and said "yea." Any reason why she's so shy around me but she can talk to everybody else just fine! Then after a while of the same thing, she started to look at me a lot today and when she would see me she would cover her head with her arms and "cuddle" on her friends shoulders. Well I asked the girl I like if everyhing was fine and she said yes, and I told her about what she did and she lied saying "no, I didn't do that". Any reason why she would lie? And what's going on?