Relationship issues. plz help?

i don't know how to ask a girl out or know if she likes me. i known this girl for 4 years and have developed feelings for her for about a month. We are quite close n sometimes i would talk to her sometimes she would talk to me both on msn n sms. i would walk with her to the train station because we take the same train but recently as we were walking we met our clmates and when we went in the station she completely avoided me by walking away and on her blog it says under her contact links 1 person loving me. im not sure if she has a bf n im too chicken to ask her out so please help... We r quite close n bicker sometimes but other then that we r fine. appreciate all comments but please be one that helps. i live in Singapore and asking a girl out may be a bit different from Western countries.