。
She seemed worried about her grades.
Literal
She [topic-は] grades [about-のことを] worried is [appearance-様子だった].
~様子だった (ようすだった) means 'seemed to be' or 'appeared to be' — 様子 means 'appearance/state,' and the sentence describes an observed impression. 成績 (せいせき) means 'grades' or 'academic results.' ~のことを心配している means 'is worried about' — の adds emotional involvement beyond plain ~を心配する.