Help me to understand this body gesture of a girl?

Hi, I talk with a girl she is only 17 & she is my neighbour. Whenever i talk with her she gives me polite reply, but she never talks to me first and our conversation is just limited to hi/hello,how are you, you look pretty etc. Today i was walking on road and saw her she was bit far from me so i did not said anything to her. After seeing me she just hidded her face with umbrella. I am really confused now, what does the face hiding sign means? I like her very much. Thank you.