K.Q.
Yes. I cannot even imagine getting high when my kids were 7-weeks old. I was so exhausted from caring for them and being up during the night, my head would be asleep before it hit the pillow; I don't think I would wake up if I was high. Plus, her judgment is impaired, so if anything were to happen, she would not be able to make the best decisions, or take the baby to the ER. Also, second-hand smoke inside the house is VERY harmful for a baby, no matter what kind. And please tell me she doesn't breastfeed...
Does she do it occasionally/socially or every night to "relax"? I would look at the underlying issues for her using drugs: Does she feel overwhelmed? Exhausted? Like she lost her freedom and this is her escape? Many new mothers feel these things. It's a major life change and she needs an outlet for her stress. She should talk to her doctor, join a gym, go for a walk. Regardless, if she is unable to stop while her child is a NEWBORN, then it is a sign she has an addiction and should seek support or develop a more supportive social circle.
(Now I am NOT anti-pot. I don't think it is really any worse than alcohol, but I do agree with the person that said it is not like having a glass of wine. You smoke to get high. And it's not like her kids are older. SEVEN WEEKS is a very delicate age. By you even posting this question, I think you know it is not normal...)