Check first at the start. Mulan is getting prepared for the matchmaker. They put on her make-up and her eye brows immediately become thinner. As soon as she wipes the makeup off in the temple her eyebrows become full again. Also, Check the comparison between her as Mulan and her as Ping. As mulan she has a round face shape, Ping has a very square shape. Also Pings eyebrows are much thicker. Then after Ping gets wounded, Mulans secret is revealed she is a girl. Ping automatically has a round face, thin eyebrows, long lashes and rosy round lips. Realistically, she should still look just like Ping with his hair down.