Was this indeed a PTO meeting, or was it a meeting for parents run by the principal? If it was merely a casual meet-and-greet sponsored by your principal and held in the school gym, then it may not have been the place to openly air your issues or concerns about the school. (Although Elly doesn’t think anyone, teachers and principals included, should ignore or heckle others!)
Your principal can speak wherever or whenever she wants in her building. Official PTO meetings, however, are generally presided over by PTO board members who follow an agenda with discussion topics. And most PTOs do follow some form of Robert’s Rules.
It couldn’t hurt to arrange a meeting with the principal to tell her about your concerns in person. If there are ways you can help address the issues you raise about the school, let the principal know you are willing and able to do so.