Advice for a friend

My bestfriend just found out she was pregnant after being a few days late for her period. She is a very heavy drinker and smokes a lot of weed and cigarettes. She said she will stop at 6 weeks when she feels she is past the chemical stage, not sure what to say to encourage her to stop sooner but did tell her the weed isn't the same anymore and cigarettes have more chemicals than in the past. She said she did the same with all her children and they are fine.