All good that.
You follow then the SI is usually driven by sort of a Pain Relief relationship (sort of a self-medication), for Emotional Hurts in the brain? Dealing with Severe Emotional Pain -- in ways OTHER than . . . . SI, Alcohol, Drugs, Eating Disorders, etc., could be a life long process and struggle for her.
Since her Biological Mother (meaning the genetics are not favorable) has such a severe Drug / Alcohol, etc., bent, it is very possible Biological Mother has these same traits, and is trapped in the destructive methods of sedating herself.
Daughter will need to learn all the coping skills in advance to stay off the destructive methods, herself.