Jus another day......

Well 2day Ive been observing my surroundings and I don't know how 2 respond its weird how people treat u 1 way when no1 is around and another when they r..... well silly me u need more details right. Well I have this friend and they r so cool and understanding when were by ourselves but when they are other people involved they act as though I am not there or always have something rude 2 say.......so is this an act of phony or is this person just ashamed 2 admit how they really feel confused ...............help! PLEASE!!!