Rude behaviour of headmistress

Hi I an writing this on behalf of my mother. She is a school teacher since 2000 and a government school teacher since 2008. Now the principal of her current working school abused my mother for not letting know of her co-staff's abscence to a training. She had no intention to save him from being caught since he pretend to work but not doing properly always. My mom's intention was to not involve in any nuisence apart from teaching. This principal commented my mother stating that she is capable of getting sevaliye award since she is like sivaji ganeshan in acting. She even stated that my mother is short in height and one should not beleive in short people words. This is rude as hell.. I am getting annoyed by that lady's behaviour but my mother is opting for a vrs since she got offended in front of everyone.. She feels mentally ill which is because of that lady's rude behaviour. I can't go against my mom's wish to bash on her and it is an offence too Right now i need a solution to be done to teach a lesson to that lady..I am seeking ur advice