Perth filly Delicacy has confirmed her staying superiority, winning at Group One level for the second time in seven days.

Taking on the colts and geldings in the South Australia Derby, Delicacy overcame mid-race interference to add the Classic to her Australasian Oaks win last week.

Her Morphettville triumphs have come after wins in the WA Oaks and WA Derby during March and April.

Backed from $2.50, Delicacy was sent out the $1.90 favourite on Saturday but she was made to work for her victory after settling at the back of the field.

Jockey Peter Hall allowed Delicacy to gradually improve until she was within striking distance of the leaders on the home turn.

From there she unwound strongly to chime in at the 100m before edging clear to win by 1-1/2 lengths.

New Zealand three-year-old Werther ($12) took second in front of Godolphin's Allergic ($18) which finished a long neck further back.

Delicacy's earnings have now swelled to $1.44 million from 10 wins in 14 starts for trainer Grant Williams and well-known Perth owner-breeder Bob Peters.