。
She is very graceful and demure.
Literal
She [topic-は] very graceful is.
おしとやか stitches the honorific お to しとやか ('graceful, refined, demure'), but the お has been fused into the word — there's no bare *しとやか in modern usage. The image is of someone with calm, refined bearing — historically a quality praised in women in Japanese tradition. The word carries gendered overtones: it's almost exclusively used to describe women, and even compliments can carry a whiff of old-fashioned expectation.