What is the most common device model among female users between the ages 27 to 28?
most common device model refers to MAX(COUNT(device_id)); female refers to gender = 'F'; between the ages 27 to 28 refers to group = 'F27-28';
SELECT T2.device_model FROM gender_age AS T1 INNER JOIN phone_brand_device_model2 AS T2 ON T1.device_id = T2.device_id WHERE T1.`group` = 'F27-28' AND T1.gender = 'F' ORDER BY T2.device_id DESC LIMIT 1