I would say Marajuana because of the number of variables and due to the fact that it is illegal, there is less research on it. Alcohol - while it is bad - is subject to regualtions, and is less likely to have as many variables. It has also had countless studies. Even though there are so many studies, they still havent figured out how much is safe, so none is best JIC.

I would have to agree with BG in that it depends on the level of addiction to each.

I do hope that she does realise that she is not only impacting her own life but her baby's too and can get rid of both addictions. All you can do though is try to keep baby's interests at heart and do what you can to give them the best chance in life.