Suggestions: Ask any callers to leave their name and contact data so someone can get back to them.
Make photocopies of whatever you believe to be an actual mail-in ballot marker and “signed” with you mother’s name by someone unknown.
Also make two scans saved as pdfs of the documents you have. Once is full for you to keep, the other with your mothers name and address and signature blocked (”redacted”). Send that to your Elections Commission and ask them to let you know whether they would consider it a legitimate ballot.
My question is - was it her ACTUAL signature?