Who is the owner of house wherein your grand mother is staying 

2if it is your grand mother house file application before senior citizen tribunal and seek orders to direct mother and sister to vacate the house 

3) if your grand mother is not owner she can file application before magistrate under DV act and seek protection order , right to stay in the house wherein she is residing and compensation for mental torture undergone by her 

4) in alternative put your grand mother in senior citizen home wherein she would be well looked after in her old age 

- You can file a complaint on behalf of your grandmother under the provision of Senior Citizens Act, to restrain them from taking her money and making her life a hell 

- Further, if your grandmother is the owner of the property , then she can evict your mother and sister from her house after filing a compliant before the same senior citizens Act, and also under the provision of Domestic Violence Act. 

Dear Client,

Report Elder Abuse: If you believe your grandmother is being mistreated, neglected, or financially exploited, you should report it to the relevant authorities. In many countries, there are agencies or hotlines dedicated to handling elder abuse cases. They can investigate and intervene to protect your grandmother's well-being.

Financial Safeguards: Take steps to protect your grandmother's finances. This may include helping her manage her pension, ensuring her accounts are secure, and monitoring her financial transactions to prevent further exploitation.

Guardianship or Conservatorship: In severe cases where your grandmother is unable to make decisions for herself, you may need to explore the possibility of guardianship or conservatorship. This legal arrangement appoints a responsible person (the guardian or conservator) to make decisions on behalf of the incapacitated individual.

Collect Evidence: Document any instances of abuse, neglect, or harassment. This may include taking photographs, keeping records of conversations, and gathering witness statements. This evidence can be valuable if legal action is needed.

Harassing a senior citizen is a criminal offence. You can ask your grandmother  to lodge an FIR. Your mother  can be booked under section 24 of the Maintenance and Welfare of Parents and Senior Citizens Act.

Also under Indian Penal Code:

Any person harassing senior citizens can be brought under Section 506 for criminal intimidation. - If the person is very abusive or utters or recites obscene words and mentally tortures senior citizens, a case under Section 294 can be bought

You can also send your complaint in writing and by post to the Superintendent of Police concerned. If the Superintendent of Police is satisfied with your complaint, he shall either investigate the case himself or order an investigation to be made.

You are bound to maintain your mother if she is unable to maintain herself 

2) senior citizen tribunal would direct you to maintain your mother pay the house rentals and give her money for living expenses 

1. If your mother is incapable of maintaining herself then it becomes your duty to provide her maintenance amount every month to the extent possible by you or the court may pass an order accordinlgy.

2. Your mother can take legal action against you for not providing her maintenance amount every month

- If she is unable to approach the police , then FIR can be lodged by you on her behalf after giving a complaint. 

1. If your mother having no sufficient income for her maintenance , then she can claim maintenance from her children including daughter

2. If she is a senior citizen , then she can approach the higher police official , however for getting permanent maintenance she will have to approach court .

-  If she files a complaint against you, then you can reply after narrating all the true facts and the said mistreat with your grandmother , and hence she may be denied to get the maintenance from you. 

In the event that your mother is unable to sustain herself, it becomes your responsibility to offer financial support on a monthly basis, to the best of your abilities. Failing to do so may result in a court order mandating such support. Your mother possesses the legal recourse to take action against you if you fail to provide the agreed-upon maintenance amount regularly.

You can disown her but as per law if she is financially weak she has right to get compensated from you 

yes she has right  for maintenance under 125 crpc