"She often studies in the library."
Translation:Ella a menudo estudia en la biblioteca.
I think I figured it out. In the first and second person (I and you), you do not have to put the pronoun in the sentence, hence a menudo goes first. In the third person where the she (ella) is used, it follows the normal word order of words like siempre and nunca. Someone correct me if I'm wrong, please.