I have to disagree with what some of the other users posted. Foster care CAN be a REALLY bad situation. I am a teacher and have known many foster kids. Although in some situations it is better than the original home, it can get worse.
The best way to see the situation is simply this: the mother in question has an illness. What is the best way to get her in treatment so that she can be the mother she wants to be to her children? Is an intervention needed? If it is, are you willing to do what it takes to get it done?
Doing the right thing is not always easy. In fact, more often than not, the right thing is down right difficult! But there are children involved, and I know they would appreciate someone stepping in to rescue not only their mother, but their family.
Panther