What is Date, when Outcome is Winner, and when Opponent is An-Sophie Mestach?
CREATE TABLE "singles_16_9_7" (
  "outcome" text,
  "date" text,
  "tournament" text,
  "surface" text,
  "opponent" text,
  "score" text
);
SELECT "date" FROM "singles_16_9_7" WHERE "outcome"='winner' AND "opponent"='an-sophie mestach';