Could be Calotis. The bracts on the back of the flower head are the right shape. However Vicflora states that there are 40-70 petals. This looks like about 30. Wait a week or two and see if it produces burrs? I have checked out several exotic white daisies. All of them had too few petals, and most had wrong shaped leaves.
I think there are several overlapping petals and the count is actually higher, particularly on the photo of the back. This is the same site as http://canberra.naturemapr.org/Community/Sightings/Details/3381712 as mine might have some GPS error. Calotis anthemoides has been reported in this area previously but usually in greater numbers.