How do I tell a girl That I like her?

My best friend recently got a girlfriend....The girl I like happens to be very close to my friend's girlfriend.....Hence my friend offered to talk to his girlfriend about this...He is saying no matter what I tell him , he is going to talk about this to his girlfriend as he wants me to be with that girl.....The girl I like talks with me everyday in my class...We are very close but I am afraid this proposal will ruin our friendship.....She tells me to shift desks in class so that I can sit and talk with her....On Valentine's day she asked for a gift...Are these signs she is giving me or just friendly gestures...I am confused and don't know what to do....plz help?