It there is no IRS records of her claiming this on her taxes and the bank has no record of issuing the proper IRS form (which the IRS should have a copy of) then the account should still be active.
Neither the bank nor IRS keeps records beyond 7 years. The IRS will have the 1040 summary for a few years beyond that, but not any detail, i.e., how much was earned in interest beyond the 7 years.