Justice Bigelow is right. Just because the parent's using drugs doesn't allow you to take their kid away. You've got to show some actual neglect of the child.
That said, Mother should still stop smoking reefer. When eight of your nine drug tests come up positive, it's a problem. When you can't stop using even after DCFS is on your butt, that's a sign -- a real, substantial sign -- that you need to get clean.
P.S. - Justice Bigelow says in the opinion: "If a parent’s failure to keep on top of a teenage child’s homework assignments is sufficient to show 'physical harm,' many, many parents would be subject to DCFS intervention." Word.