She is intonating with an intentionally more feminine accent/cadence, which may require some conscious effort if her vocal cords had already developed in a more masculine direction.

Also, most people aren’t professionals at acting, so she is probably an ameture at remembering her lines and speaking clearly enough to be understandable on-camera. After multiple takes where she found that she was stumbling and mumbling, she found the best way to be more understandable is to slow down a lot and separate her words more than she naturally would.