I have a friend with 2 adopted DDs. Their feelings about their birth mother are incredibly complicated - despite what they experienced, they still love her, she is still who they came from. Her death last year was devastating, as the older DD especially wanted to meet her and ask questions (not only the 'why'?, but also questions about her earliest life that only her birth mother could have answered) and express her anger about what had happened. The older DD has even more sadness and anger now, as BM's chaotic and addicted lifestyle contributed to her early death.
What she did was horrendous, and she got the punishment that society has chosen as the 'least worst' option - given nothing can undo what she did. Perhaps she felt guilt and remorse, perhaps she didn't.
Let s/he who is without sin cast the first stone. There are no 'winners' with her death.