Okay well, if you know about this it is kind of your job as a human being to do something about it. I mean the government isn't always the best way to go, but in this case you have to call social services. I mean what if the 8 month old, one day found some crack and decided to taste it. I hate to say it that would kill her, and then your friend would be going to jail on counts of, contributing to the deliquence (sp?) of a juvenile, child endangerment, drug charges, and if god forbid the baby did pass, possibly homicide or manslaughter.
So I know it may be hard to do, but sit down and talk to her, try to find some programs that can help, and if she doesn't cooperate right now call the police or social services.