Some people confuse hope with reality so thoroughly that they start treating their own wishful thinking as an official plan. That seems to be exactly what happened here

A woman finds out, secondhand, that her mother and stepfather have been telling people he will walk her down the aisle at her wedding. The catch is that no one ever asked her, and nothing in their relationship suggests this was ever on the table. She met him as a teenager, never saw him as a father figure, and has kept things polite but clearly platonic for years. Somehow, that got translated into an assumed tradition