21 years ago, the effects of smoke on babies intrauterinely weren't as well known or accepted, dark lord. my husbands parents smoked while pregnant, and weren't told to stop either. and we all know for a fact cigarette smoke is much more dangerous than marijuana
personally, i smoked a few times, when the nausea and headaches were really bad. I am not a pot head, never have been, it was purely medicinal. i felt it to be safer not to mention more effective than the drugs the doc gave me.
my recomendations, haibane, would be to only smoke at night, after the last feeding. and if possible, express a few times before the feeding in the morning. But I dont know how long the thc takes to leave teh system through the breatst milk, some googling of medical studies would be prudent for you and her to do.
frankly, a bit of THC in breast milk is still better than the shit you get in the bottle, imnsho