。
I'm sure she'll arrive on time.
Literal
She [topic-は] surely time [in-accordance-with-どおりに] will-come [probably-だろう].
時間どおりに ('on time, punctually') uses the suffix ~どおり / ~通り ('exactly as, in accordance with'), attached to nouns to mean 'just as X.' Other examples: 予定通り ('as planned'), 言われた通り ('just as I was told'), 約束どおり ('as promised'). The ~に at the end makes the whole phrase adverbial, modifying 来る. Punctuality (時間厳守) is a culturally weighty topic in Japan — being late, even by a few minutes, is treated as a meaningful breach of trust in business and personal contexts alike, so 'showing up on time' is rarely just a logistic detail.