She searched for her granddaughter who had been taken away.
Literal
She [topic-は] taken-away granddaughter [object-を] searched-for.
連れ去られた is the passive past of the compound verb 連れ去る ('to take away, abduct') — 連れる ('take along') + 去る ('leave'). It functions as a relative clause modifying 孫娘 (まごむすめ, 'granddaughter'). The sentence has a narrative or news-reporting quality.