For my friend's friendship with her best friend.

let it go if it hurts too much
friendship should not be tiring you out in the first place.

let it leave if it happens as such
before it gets you down and totally crazed.

let it be if you can
friendship should not be kept just because it has been a long time.

let it move away as and when
for it is her loss and only then will she start to pine.

You will be fine.