What was the score of the final in which Melanie South played with partner Katie O'Brien?
CREATE TABLE "doubles_24_21" (
  "outcome" text,
  "tournament" text,
  "surface" text,
  "partner" text,
  "opponent_in_the_final" text,
  "score" text
);
SELECT "score" FROM "doubles_24_21" WHERE "partner"='katie o''brien';