This is what it probably was. I honestly did anything and everything I could for her but she continued to fall away and I was at a loss for what to do.
That's okay. You don't need to blame yourself for not knowing what to do in that situation, because most of us don't, but if there's anyone you can't blame it's her. Depression is a sickness and a potentially fatal one at that, it's not something to be taken lightly.