I cut this in a garden recently. The owner said it was a var of Aster. The bush was about 5' tall. She thought it was a Florida native. I could not find any Florida native Aster that looked like this.
In my picture the petals are slightly lighter and in reality should be slightly more violet than shown, but not as dark as the closed flower (extreme left side) also shown. The flower is about 1/2 inch in diameter.
I would say it's not the Brachyscome. The petals of all the Brachyscome listed here are nice neat petals. In my picture the petals are all skewered and not nice and neat looking as are the Brachyscome. All the blooms so far have looked like the one in my picture. None have appeared neat and orderly. Another point, mine came from a bush that was about 5 feet tall and about 4 feet wide. It was full of branches containing lots of these little flowers. Even though the bush had lots of flowers and small leaves, it looked almost bare for it's size.