A butterfly's truth

Amber and Ava were inseparable since day one, sixteen years later Ava finds herself facing the steely truth that her oldest friend took her own life.

While Ava struggles with self-blame, loss and regret while preparing to accept the unfathomable.
Amber's story is also slowly uncovered, events that began when she was thirteen and continued onwards for three years.

How did two people who appeared to be almost identical in the beginning - finish in entirely different situations by the end.