This is like the mother who claimed fool because her kid was allergic to peanut butter so she wanted the school to ban everyone from having it.
I think she might have a good cause for a wrongful firing lawsuit since smoking is legal. Yes it is banned in certain areas but no where does it say it is illegal to smoke.
The right thing to do would have been give her a different assignment within the school or perhaps transfering the student but that makes too much sense.