Thank you, greeteachday. Those are some excellent suggestions! Although it's difficult to accept, my NarAnon and AlAnon programs have taught me that I cannot compel her or my dad to action or change by abstaining from contact. I think that's why I feel like I'm facing two equally bad choices: (1) Cut off ties knowing that she's probably never going to get help. This has the advantage of getting me off the roller-coaster, but the distinct disadvantage of inflicting feelings of sadness, abandonment, and loneliness that aren't really necessary (in other words, a lot of times things between me and my parents can be really great)
OR (2) Continue contact knowing that she's probably never going to admit she has a problem or get help. This has the advantage of salvaging what up has been, for the vast majority of my life, my most fulfilling and joyful relationships. But then I'm back on the roller-coaster.
In sum, option (1) will be a lot of
and option (2) will be a lot of
. I guess I'm really trying to determine which has less net negative impact on me.