You are in a way lucky, in that an ordinary aerobic exercise and reduced calorie diet regime will tend to preferentially reduce the fat from the waist while preserving the fat deposits around the buttocks, hips and thighs (due to standard mature female genetics).
Also, avoid all alcohol as that tends to increase the "visceral fat" deposited around the internal organs (hence causing the so called "beer belly prevalent among heavy drinkers).
-- Best wishes - Majikthise.
try this program called p90x and do the specific "ab ripper" version as it only focuses on your waist
You can try bending from side to side everyday, or twisting for about like half an hour?
Try swimming- great exercise...