。
She said she'd come right back.
Literal
She [topic-は] soon return-come [quotative-と] said.
戻って来る ('come back') chains 戻る ('return') with 来る ('come') via the te-form. The full compound emphasizes the direction of return — back toward the speaker's location — whereas plain 戻る would just say 'return' without the inward orientation. ~てくる as an auxiliary is the directional 'come / return toward me' partner of ~ていく ('go away / continue forward'). The と + 言った frames it as reported speech.