。
She goes to that bookstore once a week.
Literal
She [topic-は] week [per-に] once that bookstore [to-に] goes.
書店 (しょてん) is the formal word for bookstore — more written-register than the casual 本屋 (ほんや). その (that) points to a specific, known bookstore. The frequency expression 週に１度 and the habitual present tense 行く describe a regular routine.