Green’s Dictionary of Slang

(Aus.) a woman dressed up in a (fashionable) frock; thus frocky adj., fashionably dressed.

1901		Bulletin (Sydney) 16 Nov. 12/3: Mrs. Burdekin again kept to the fore of frockers. She showed the curviest figure on the Terrace, and her cream frock was braided down and slashed across to accent the curve in at the waist.
1902		Bulletin (Sydney) 13 Sept. 14/3: On Saturday Mrs. Chadwick was the most frocky of the fashionables, in blotting-paper pink and modish black.
1910		Bulletin (Sydney) 13 Oct. 20/2: Mrs. Hugh MacNeil, the golfer and one of our smartest frockers, had gotten herself into the most delicate of greenish greys, in a material that might have been a cloth, but which looked like satin.