。
She always goes to church on Sundays.
Literal
She [topic-は] Sunday [topic+contrast-には] without-fail church [to-に] goes.
には is a stack: time-marker に + topic/contrast は. Together they pick out 'as for Sundays (specifically)' — restricting the generalization. 必ず ('without fail, certainly') is a strong adverb for absolute regularity. 教会 ('church') refers to a Christian church specifically, while a non-Christian temple would be 寺 or 神社.