The criminal proceeding under the Domestic Violence Act (DV Act) initiates by moving a complaint under Section 12 of the DV Act. It is a complaint case and the Magistrate, after perusal of the content and evidence of the complaint issue process (summon or warrant) under Section 204 of the Code of Criminal Procedure (crpc).
At the stage of issuance of process, the court has to examine the facts of the case and evidence adduced by the complainant. If the court finds that there is sufficient grounds to proceed further against the accused then he issues summons [Dr. C. Abraham vs Maulavi 1990 CrLJ 533].
Magistrate has to issue summon if prima facie offence is made out
If you have successfully proved that the prima facie offence is made out against the accused including the sister in law, the Magistrate has to issue process. The Magistrate cannot evaluate or appreciate evidence and facts in a detailed manner for the issuing process.
If the sister in law has committed an act of domestic violence the aggrieved person has right to file a complaint against the sister in law.
High Court can direct the Magistrate to issue summon
If you are feeling aggrieved because the Magistrate despite having prima facie case against the sister in law not issuing summons then you can move a petition before the High Court under Section 482 crpc for directing the Magistrate to issue summons.
Otherwise, you should wait till the initiation of trial. If during the trial you produce enough materials against the sister in law that she has committed an act of domestic violence, then the court will be bound to issue summons.
At that stage you should move an application under Section 319 crpc for calling your sister in law as an accused. The court after appreciation of evidence shall issue a summons against your sister in law.