This is exactly what happened between my darling best friend and I in our 20's.  She broke up with me after putting up with my awful on again off again relationship for many years, she could see what it was doing to me and couldn't watch it anymore.  I missed her more than I can say and it really opened my eyes.  Our reunion a year later was one of the best days of my life and we had many more years of best friendship until 2 years ago when she passed away suddenly.  I know she did what she did to kick my butt into wanting better for myself which it most certainly did.  Cherish your best friends, be there for them and love them fiercely, for they are the family you choose for yourself.