the cub in the end was a girl. it had NO fruit juice on before it was raised. kiara got it after she was raised not BEFORE. simba was the only one that had the juice on his head BEFORE he was raised. because the cub in the end lacked the fruit juice before it was raised , that makes it kiara , or a girl.
so look at this equation
fruit juice before raised = male
fruit juice after raised = female
fruit juice not on forehead =female [ meaning she's gonna get it after she was raised.]
and also , at the end credits , after the cub is raised , you can hear a boom , and the sound of a fruit crack , where as , with simba after he was presented , it was just a big boom. no fruit crack.