If the situation is no more tolerable and if you feel that it will no more be possible to live together with him in the marital relationship with him, then if he agrees for khula, you can given khula, or you can file a divorce case on the grounds of cruelty under section of Muslim marriage act, 1939.

As the child is under your care and custody, if at all he seeks child custody, let him approach court for the same, because there is no provision in law for a Muslim to seek child custody though he can claim guardianship over the child under guardians and wards act

File a domestic violence case against him and his family members immediately. Ask for a KHULA which can be demanded as per the sharia law.

Maintenance application should also be filed against him.

Full maintenance and alimony should be demanded although in khula you have to forego the mehr.

- Firstly you should know that for your sister Divorce will be not a better result for her future. Hence, before taking Divorce decisions, she is having the following right and claims from her husband. 

1. As per law, A wife has the right to claim decent living standards and basic comforts of life from her husband. Hence for claiming the maintenance for her & child, she should file a petition under section 125 CrPc.

- Her husband is under legal obligation to provide the same to her at any cost, even he is working or not. 

2. Law entitles wives a basic right to reside in the matrimonial/ home, whether the house owned by her husband or his parents, a rented property or officially provided to him. 

- Hence, for claiming her residential right, medical expenses etc, and also for teaching a lesson to the family members of her husband, who subjected her torture & harassment, she should file a petition under the provisions of Domestic Violence Act.

3. As per the Supreme Court, A wife has complete ownership rights over all her Streedhan, the gifts and money given to her before and after marriage. The denial of Streedhan to the wife makes the husband and in-laws liable for criminal charges. 

- And further, if the husband or his family members subjected a woman to cruelty for the dowry demand, then they can be booked under Section 498-A.

- Your sister should lodge a written complaint against her husband & his family members, in the Women cell/Mahila Police, after mentioning all the details of torture & harassment. 

- The women cell firstly will try to reconcile between them, otherwise, they will lodge an FIR against all the person, who subjected your sister cruelty. 

- Further, if you don’t want to create problems for your sister’s husband, and proceed for divorce, then you can get divorce decree within a short period of time, after filing mutual divorce petition under Muslim Law. 

You can contact me , if further details suggestion needed. 

You should reply to legal notice 

2) file for divorce on grounds of cruelty 

3) seek interim maintenance and alimony from husband 

4) also custody of your child 

1. If you have received a lawyer's notice then it is imperative that you must answer it through your lawyer.

2. If the legal notice goes unanswered then it is tantamount to admission of allegations.

3. Your sister is free to file complaint case under Section 12 of DV Act, 2005 to seek compensation, maintenance for herself and her child and also child custody.

4. She is also free to apply for divorce.