How do you win your best friend back?

Okay...so i sort of had the same problem when i was in middle school.. things change and so do people.. if i were you i would ask just Denise to hang out with you and have like a sleepover and talk to her about whats bothering you and how you always feel like the third wheel..if she does something about and really tries then you know that she really cares about you and your feelings but if shes just like whatever, then move on and make new friends...