。
She let go of the boy.
Literal
She [topic-は] boy [object-を] released.
放す is the transitive 'release / let go of / set free,' contrasting with the intransitive 離れる ('separate / move away'). Without further context this could be physical release (letting go of someone's hand or arm) or freeing — Japanese leaves the situational nuance to the surrounding discourse, where English would often pick a more specific verb.