Once upon a time, my driver's ed teacher told me "forget the rule book for a minute... just stay farthest away from the most immediate threat." Sometimes that meant hugging the edge of a road on a blind turn. Other times that meant moving almost to the center of the asphalt to stay away from a steep dropoff at speed. (Hey, I grew up in East Tennessee mountain area, the back roads are... interesting)
Anyhow.. that's always seemed a pretty good life philisophy to me.
As described, this woman is a greater threat to herself and those around her with a firearm than without. In keeping with the principle of "stay futherst away from the most immediate threat" -- don't bring a weapon into her life. There's not a chance in heck I'd help her arm herself.
Further, to be brutally callous... some of Darwin's children are desperately begging to be called home. If her behavior is that self destructive... I'd be inclined to let her reap what she's sown. But then, I've had more than my fill of drug-abusing, criminal-associating, blankety-blanks lately.
-K