Smoking marijuana n breastfeeding???good or bad?

okay before people start going crazy on me for the question i asked!!ITS NOT FOR ME!!!! i have a friend who wants to start smoking again but is breastfeeding a 6 1/2 month old baby!!!she asked me to research this for her n i did!!all i found out was that some say its bad others with experience say otherwise.i looked up this article about mothers in jamaica smoking while pregnant n it say marijuana smoking didn't harm there newborn n they were as normal as can be. and cannabis websites say the same thing that babies are actually smarter n more advanced then other babies who parents didn't use marijuana!!So people with EXPERIENCE PLEASE comment below pros n cons!!!PLEASE people without experience n just have there own opinions about this dont bother writting!! I really want people that actually gone through something like this to answer!!!THANK YOU!!!