That is heartbreaking. My 23 year old son said something similar not too long ago and I realized that it does not matter that he is an adult.It still hurts when you feel your parent has left you for the alcohol. And yes I still felt pangs of guilt although I know there is nothing I could have done. I told him that I prayed to God everyday to keep him safe and give him health-physical, emotional, and spiritual. We just needed to take care of ourselves and live our lives in a healthy way, enjoy the good thing we still had in our lives. Be grateful for our own health.
Hugs to you. The pain she feels and can share with you is much better than the pain of growing up with an A and all the secrets, cover up and distorted relationships.