Yes, unfortunately you are required to attend the 2004 Examination, or you could be held in contempt of court. Rule 2004 authorizes, among other things, the examination of an entity relating to "any matter which may affect the administration of the debtor's estate," not just the Debtor. Courts have consistently held that a bankruptcy petition preparer "may affect the administration of the debtor's estate."
As a practical matter, the Debtor was allowed to FILE a second Chapter 7 within the eight-year period following her first discharge; however, she would not be eligible to receive a second discharge. There might be some valid reasons to file a second Chapter 7 regardless of the fact that she couldn't obtain another discharge (i.e. to obtain the benefit of the automatic stay for a few months).
From what you stated, it appears you may have a legal problem, which could be why you were subpoenaed for the 2004 Examination. When you accept money from a Chapter 7 Debtor to prepare a bankruptcy petition, you MUST submit a DECLARATION AND SIGNATURE OF NON-ATTORNEY BANKRUPTCY PETITION PREPARER, here: http://www.uscourts.gov/uscourts/RulesAndPolicies/rules/BK_Forms_1207/B_019_1207f.pdf and a DISCLOSURE OF COMPENSATION OF BANKRUPTCY PETITION PREPARER, here: http://www.uscourts.gov/uscourts/RulesAndPolicies/rules/Revised_Rules_and_Forms/b280_1207.pdf. Pursuant to Section 110(a) of the Bankruptcy Code, you could be required to pay the Debtor statutory damages of up to $2,000 for this violation. Your fees from other cases where you failed to make the required disclosures may also be disgorged, and you could potentially be liable for statutory damages in these cases as well.
In light of all of this, you may wish to retain a local attorney to help you with this matter, as the Court will presumably attempt to clawback the money you received from ALL of the cases for which you did not file these required disclosures.