She's not actually asking for 2-for-1, she's asking about applying the value of the Ticketmania ticket and her already paid for
DVC AP voucher and upgrading to a PAP.
Yes, you can do that since you are only applying the value of a single ticket to the transaction. Remember that the AP voucher is treated the same way as if she had an active AP and wanted to upgrade it to a PAP. She can apply the DQ ticket to it in either scenario.