In the female customers, how many bought root beer that contains artificial sweetener?
female refers to Gender = 'F'; contains artificial sweetener refers to ArtificialSweetener = 'TRUE';
SELECT COUNT(T1.CustomerID) FROM customers AS T1 INNER JOIN `transaction` AS T2 ON T1.CustomerID = T2.CustomerID INNER JOIN rootbeer AS T3 ON T2.RootBeerID = T3.RootBeerID INNER JOIN rootbeerbrand AS T4 ON T3.BrandID = T4.BrandID WHERE T1.Gender = 'F' AND T4.ArtificialSweetener = 'TRUE'