IMO, the response had nothing to do with the teacher "being in NA"...
My daughter is 13 and has been dancing for 8 hours a week for over 5 years... Her teacher has said the same thing to her and the other students in the class... Were you there when the teacher made the remark? I know being a parent of a pre-teen/teen that girls tend to over-react to how things are said to them... I wouldn't make a decision to pull my child based on one remark, even if the teacher was practicing the steps of NA...
I am not being insensitive to the situation, just reacting to MY instincts as a parent of a teen myself.....