Mrs Williams, one of the loudest voices throughout the campaign for justice following the 1989 football stadium disaster, is being remembered at a service in Formby.
She died aged 62 on Thursday April 18 after a battle with cancer.
Scores of people, many wearing Liverpool scarves, gathered in bright sunshine outside Our Lady of Compassion Church.
A hush fell over the street as the hearse bearing Mrs Williams' coffin pulled up.
It also contained a wreath of white flowers embellished with red roses that spelled out "Mum".
Bystanders watched as the coffin was carried into the church, followed by hundreds of mourners.
Mrs Williams spent almost half her life campaigning after her 15-year-old son Kevin died in the Hillsborough tragedy.
It was her fight to get his inquest verdict of accidental death overturned that is credited with leading to fresh hearings for all 96 supporters who died.
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