What to do when you're sick of your life?

To start with,I am 15 years old. I ve got lots of friends.I can say I'm quite famous. I ve also got a best friend . She's really good,we have so much fun together, but since I started feeling that I don t want her to be around anymore. We only have fun together,she s not listening to me,and she's never around when I need her. We can t go shopping together at the places I want to go,cause she can t afford the stuff. She s not interested in my activities and she doesn't like the things I mad about. She treats weird to new people,and being with her,lots of them,may think that I act like this too... I don t want to leave her,we have so much fun together,we laugh all the time. I know,life isn't just fooling around,but I feel comfortable with her,I can tell her everything... Should I leave her? And if so,How can I leave her without hurting her feelings?;/ I feel like a terrible person please help meee;/