。
She'll be back at 5 o'clock.
Literal
She [topic-は] 5-o'clock [at-に] returns-and-comes.
戻ってくる ('come back, return [hither]') uses ~てくる to mark motion toward the speaker — she will return to where the speaker is. 戻る ('return') is more neutral than 帰る ('go home'); it marks return to any prior location, not specifically home. The polite ~ます form fits the everyday register of telling someone when to expect a return. 五時 ('5 o'clock') uses 時 as the counter for clock hours.