The Irish model and DJ, who was first romantically linked to former boyband singer McFadden in May, said that she will return home for a month to see family and stock up on chocolate and clothes before returning to Sydney for a year.
Williams told the Herald Sun: "Oh my God, I just love it. I only meant to come out for a couple of weeks and it has just been brilliant.
"I have to go home for a month over August, but all being well I want to come back in September for a year. It seems to be the thing to do when you finish college in Ireland, but I never did [a gap year] so it would be my chance."
Williams said that she would "rather not" share details of her relationship with McFadden but did admit that she would play some of his songs during her first Australian DJ set this Saturday night.
"I'm not sure if he's coming," she revealed. "But I've always liked his music. I'm planning to stick to sort of pop and a little bit of electro."
McFadden split from Delta Goodrem shortly before he was first linked to Williams. She is now believed to be dating US singer Nick Jonas, but McFadden said last month that Jonas would be "dead" if he hurts her.
Watch Brian McFadden's 'Mistakes' music video below: