The best thing would be to get a bankruptcy lawyer now and have the lawyer handle it. The lawyer can probably get it done with a call. Once the bankruptcy is filed they are no longer legally allowed to subpoena her. So that is the first priority.
This is not legal advice. You should always discuss the specifics of your issue in person with an attorney. Be aware that there are time limits on all claims that depend on the kind of claim, so do not delay in seeking an attorney.
I agree with Mr. Arbuckle.
Your sister should not try to handle this herself by calling the clerk or anyone else. She needs a lawyer, probably a consumer bankruptcy one, for this. No, sending the clerk documents, such as food stamps, will not accomplish anything. A subpoena is a court order to appear in court in person. Failing to appear in person can land your sister in jail.
I wish your sister good luck.