Write SQL query to solve given problem: How many female students have enlisted for the Army?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT SUM(IIF(T3.name IS NULL, 1, 0)) AS "result" FROM enlist AS T1 INNER JOIN person AS T2 ON T1.name = T2.name LEFT JOIN male AS T3 ON T2.name = T3.name WHERE T1.organ = 'army'