。
She fainted upon hearing the dreadful news.
Literal
She [topic-は] that dreadful news [object-を] heard-and consciousness [object-を] lost.
気を失う ('to lose one's spirit') is the standard idiom for fainting or losing consciousness — Japanese frames consciousness as 気, the same word for 'mood, energy, intent' that runs through hundreds of expressions like 気をつける ('be careful') and 気にする ('worry about'). The ~て form chains hearing to fainting in tight cause-and-consequence: 聞いて → 気を失った. 恐ろしい is a notch stronger than 怖い, with overtones of horror or dread rather than ordinary fear — fittingly grand vocabulary for news that knocks you out cold.