I am so sorry. I can feel your frustration and hopelessness. You know what you need to do.....
You cannot love them better. You did not cause this. You cannot control this. You cannot cure this. It is common for those with advanced alcoholism to say they don't want to live anymore. But you don't have the tools to deal with these feelings of hers. It is not your job. She needs help. SHE needs to be the one to get it.
I was in your shoes in May. I left our home, worked on my serenity. He died in July. It breaks my heart every day. But, it was his choice. I paid the house payment, all the bills, even offered to pay for 50k worth of rehab. Made no difference.
Focus on YOU. Take care of you...just for today. If you are open to it, find an alanon meeting. Read all you can. You are loved and cared for here.