Im having a problem with a.............F*R*I*E*N*D!?!?

I have known this girl for about 2 and half years now. We are friends but it seems to be drifting off a little bit, kind of. So I'll give you a little background on what shes been doing. Her name is Halle by the way, and we WERE really close friends tell each other secrets always having sleepovers etc. Now that she has met my cousin (brianna) and my other friends its not so much like it used to be. For an example- Halle almost trys to be a different person to them and other people at school. Halle with ignore me totally like im not there, and when im talking to our whole group of friends she will cut me off and start talking about what she wants to talk about. And Halle knows that i was talking. It seems to me that she wants people to feel bad for her all the dam time. Also it seems like Halle ALWAYS has another sob story to tell, so everyone will go aww no. ITs annoying and gets old after a while. And the last thing that I can think of is, she'll try to make herself better looking than me. For an example- she was in the same class as me freshman year. Its summer right now! but anyways we had to draw a zoo and measure and all that crap, but I was done with mine and a lot of people were saying mine was really good and the teacher really liked it and ladeeda. To get to the point she whipped out her zoo and tried to show everyone how good her zoo was. Things like that Halle will do, its annoying. And I'll be telling something that happened to me she'll Cut me off and have to tell something that happened to her that makes her look better. Its hard to explain but if anyone has ANYTHING! PLEASE HELP!!! Im about to yell at her sometimes.................sorry for the long details but I had a lot to say. Hope you can help thanks :)