Actually three.
I suppose what I am trying to say is that if your friend is taking a gamble. Maybe a baby might be the makiing of her. But if she takes risks with drink and drugs, she will not have the cute, happy baby she wants. She could have a very disformed and disabled baby who will make huge demands on her.
Disabled babies can bring many rewards. But I do not think any parent in the world would not admit they are hard work, draining and demanding.
Most patients would want their child to be happy and healthy and be able to play, swim, go to scholl, grow up and get married. No ten year old would ask to be in diapers, or unable to sit up on their own.
It might not happen, but it could so why take the risk.
I think that if you tell her this and inform her, then you have done all you ca, and might be able to feel at peace with yourself. You did all you could.