Can't understand really what's going on!

So the problem is that my friend(or ex friend or I don't know how to call her) doesn't want to be with me anymore. From the first grade we have been together,going out together and having fun together. but about a year ago she got on with our new clmate. Actually I'm in a good terms with her too. All the time she is with her. She calls her more often than me,they are like twins. When I started investigating what was going on between me and her, she got so surprised and denied that something was wrong with our relationship.Then we kind of break out and had a conflict.After all we got on again and were kind of OK, but now here you are she and her NEW friend went to the countryside and had a great time, consequently she again forgot about me and still we can't break the ice between us! What I've got to do?