re: My worst fear came true.

Your description of her and all you've been through with/for her says she makes poor choices and is a mess. It was noble of you to try and help her, but stop beating yourself up over her. She will not get better. You were probably the most honorable human being in her life, but she just refuses to be worthy. She isn't willing to put forth the effort it takes to be respectable and responsible. Be proud you tried, but move on and try to stop looking back.
I've been there buddy.