Arlene was 15, when she vanished near her home in Castlederg, after attending a disco at Bundoran in Donegal with friends in August 1994.
Her family now fear new “presumption of death” legislation, is being used to stall the probe into her murder.
A hearing under the new law will be held in Belfast next week.
Convicted child killer and rapist Robert Howard was acquitted of her murder, but his criminal record were subject to a publicity ban throughout his two years of court appearances in Northern Ireland.
Arlene’s sister Kathleen says the family wants the inquest to resume. “We want justice for Arlene,” she said, adding that the family want her body found and details of how she met her death.