You cannot initiate any action on behalf of your mother.

Only your mother cant take proper action against the tortures meted out to her by her colleague.

Your mother may first directly warn that lady colleague about this and may ask her to refrain from making such charges.

If she is not listening or retaliates of aggravates the situation, your mother may file a written complaint against her with the principal/headmaster of the school narrating the entire incidences seeking to initiate appropriate disciplinary action against the erring staff. If the HM is also not initiating any proper action against her, then your mother may make a written complaint with the Chief education officer and seek his intervention.

Since this is a local and internal matter, a complaint with the police at this stage may not be maintainable.

1. Ask your mother to collect evidence of her such abusive and torturous behaviour by audio/video taping the conversations,

2. If such act of that lady falls under the category of offence to be charged with the sections of Indian penal Code, then your mother should lodge a police complaint against her submitting the said evidence in support of her allegation,

3. If police refuses to act within a reasonable period of time, your mother should file a writ Petition before the High Court against police inaction.

first of file a complaint before the department and if no action was taken by the department then file a civil suit for injunction before civil court to prevent her to do illegal and immoral activities against your mother along with a compensation due to damage of reputation.

Feel Free to call

It is only your mother who can take legal action through an injunction to stop her colleague from defaming her. She can also file a criminal case for defamation against her if she can prove that she suffered a loss of reputation due to the acts of her colleague.

first you may file complaint before superior officer because it is necessary to claim any legal right that official / departmental recourse has been taken.

if you give some more detail about your case so it'll be good for us to guide.