Smoking

Can you smoke weed when your breast feeding? I was a smoker before I got pregnant and I was going to continue to smoke after the pregnancy. ( if I wasn't going to bf ) but I want to breast feed so I just figured I wouldn't smoke and to breast feed instead. however my sister is trying to say you can smoke weed and breastfeed because it's not like cigarettes where the baby can get nicotine from it. I don't believe what she's saying is true and is calling me a prude for not doing so.