。
She didn't take advantage of the opportunity.
Literal
She [topic-は] good-opportunity [object-を] did-not-use.
好機 ('good opportunity, chance') is a Sino-Japanese compound — 好 ('good') + 機 ('chance, occasion'). Slightly more formal than the everyday チャンス, with a hint of weighed evaluation. 利用する ('use, take advantage of') aligns naturally with this kind of strategic-sounding noun. The negative 利用しなかった ('didn't use') frames the lost opportunity. The rhetoric of opportunity (機会, 好機, チャンス) is everywhere in business and self-improvement vocabulary.