Still hiding half of her face behind her guitar is a famous sentence in Bai Juyi's poem Pipa, which was originally written about the shyness of pipa girls when they came out.
Later, it is often used to describe a woman's shyness, which is extended to ambiguity, cover-up and fear of exposure.
Still hiding half her face behind her guitar from us "is often used to describe a girl's shyness." It can also mean that a thing can't see clearly and doesn't know the direction.