Me and my gf were goin fine no problems happy as can be all of a sudden she starts ignoring me read details?

its a very long story so ill shorten it up ummmm the last cople days my gf was actin really weird not eve lookin me in the eye or smilin at me and refusing to admit something was wrong and we went on the rooter bus last night for the whole nine hours we were there she said maybe ten words to me. so we are gettin off the bus and she just like walks away so i said hey do i atleast get a hug i wont see you for a week she looks at me for a couple seconds turns around and walks off without sayin a word to me. hasnt talked to me since. if anybody can help me id like some hellp