This is about my best friend... can you please help?

Last year, my BFF since 4th grade, we had no cles together except one. It's the same this year! Eighth grade just like seventh grade. She has every cl with this other girl that i used to be friends with in third grade. Now they have sleepovers and she's her other best friend. We don't fight it's just that she acts different around her. Me and my BFF still have sleepovers it's just that I want to have a get together before school, and she's going to Stacy's when Stacy just came over last week? What should i tell her?