。
She replied to me right away.
Literal
She [topic-は] soon reply [object-を] gave-me.
返事をくれた ('she replied to me') uses the giving verb くれる to encode that the reply came toward the speaker — the recipient is implicit because くれる always points inward. The literal pattern is 返事 ('reply') as an object she 'gave' the speaker, treating the response itself as a kind of gift. Without くれる, the more neutral verb 返事をした ('she replied') would lose that benefactive flavor — the warmth of acknowledging the favor.