tā / yòng / zhōng / zhǐ / mǔ / qīng / qīng / àn / xià / le / shǒu / jī / píng / mù / shàng / de / àn / niǔ

她用中指拇轻轻按下了手机屏幕上的按钮。

She gently pressed the button on the phone screen with her middle finger.