I have to be in agreement with everyone else - maintaining professionalism is something that has to be done as long as the contact is made while you are in your role.  However, should she ever confront you outside of your role - i.e, the supermarket, post office, etc - then I'd say you could have a say in your opinion on what's been going on.  But some may even argue that you should stay professional even in that situation.

Out of curiosity - is this the woman's first child going to school?  Sounds like she's taking the extreme in being over protective.

Let us know how things work out....