How long was Kendall Allen's complaint about her credit card?
how long refers to ser_time; credit card refers to Product = 'Credit Card';
SELECT T3.ser_time FROM events AS T1 INNER JOIN client AS T2 ON T1.Client_ID = T2.client_id INNER JOIN callcenterlogs AS T3 ON T1.`Complaint ID` = T3.`Complaint ID` WHERE T2.first = 'Kendall' AND T2.last = 'Allen' AND T2.sex = 'Female' AND T1.Product = 'Credit card'