A former resident of a Catholic Church institution says she was called a "filthy little liar" and forced to take multiple large doses of castor oil as punishment for reporting repeated sexual abuse by a priest.

The woman, who cannot be named, was giving evidence in the trial of Finian Egan, a 78-year-old former priest and youth worker who worked at multiple dioceses across NSW in a career spanning more than 30 years.

Egan is now facing eight counts of indecent assault and one count of rape in relation to a series of alleged attacks on four girls aged 10 to 17 in the 1960s, 1970s and 1990s.

Egan has pleaded not guilty to the charges.

Fighting back tears, the woman told the Downing Centre District Court on Monday that she was first assaulted by Egan in March 1961 when she was sent to St Martha's Institution for Disadvantaged Children in Leichhardt at the age of 10.