It looks like she had been fighting depression most of her life and finally gave into the only way she saw out of it. The fact she did it right before she was to be inducted into the Country Music HOF is significant. As many of the name celebrities seem to choose that point in which most of us would feel we have arrived.
She was being inducted and planning a tour and must have felt if that can break this curse, what can? Is this all there is?
Unfortunately, mental illness is not treated as a disease by the masses because unless they've felt it, can't understand what it is. And it seems to me that the more we make technological progress and move forward, the more we leave those fighting this behind.
Very sad for her daughters and family as they can't escape the feeling they could have done something. On the other side of that is the fact she lived with this her whole life and lasted until she was 76. Some things in life have a rather convoluted way of being grateful.