。
She prepared for an emergency.
Literal
She [topic-は] critical situation [for-に] prepared.
危急 ('pressing, critical, urgent') is a Sino-Japanese compound — 危 ('danger') + 急 ('urgent') — shading 'urgent danger' with a touch of formal-register weight. 事態 ('situation, state of affairs') is a high-register noun that often carries the connotation of trouble: 緊急事態 ('emergency'), 異常事態 ('abnormal situation'), 非常事態 ('emergency state'). Pair the two and you get a phrasing that sounds at home in news, government statements, or formal writing. に備える ('prepare for') takes に for what's being prepared against.