Sections under IPC & other law codes / acts protecting ladies from being mentally harassed

Wanted to know Sections under IPC & other law codes / acts under which a man can be punished for mentally harassing a lady, via written messages in WhatsApp groups and emails and via one to one verbal dialogues & for maliciously framing her for actions which were not done intentionally? To bring more clarity over the issue, my mother been assisting society residents in picking up & dropping off kids (2-3 years) to their nursery school (alongwith my daughter) in a private school van arranged collectively by the parents in the society. Lately, one of the parent was unhappy with her and started blaming her for the delays in pick-up and drops instead of the van driver. Although my mother had been performing this service out of affection with no money involved in it, but now this family started treating her like maid from the school, and started blaming her for every other mishappening with their kid (even if the same happened as a cause of their negligence). With respect to this all the other parents decided to disbar their kid from the school van services, as mostly all of them are working professionals and were courteous towards my mother for this service. Post this act, the family accused my mother for disbarring the kid from the van's services, which was a collective decision of all the parents. Since then the gentleman alongwith his entire family had been threatening us to file cases against my mother for child abuse and mental harassment. We had been receiving threatenings via whatsapp messages, emails and even phone calls now. They shout at her every morning and noon in front of the kids in the van. Please guide us how to stop this, as we tried speaking to them but this isn't stopping.