。
She fell into a panic on hearing the news.
Literal
She [topic-は] that news [object-を] hearing [then-て] flustered-fluttered.
慌てふためく is a vivid compound verb — 慌てる ('be flustered') + ふためく (a verb form related to fluttering, from a related root with 羽 'wing/feather' imagery) — meaning to flap about in panic, lose all composure. More dramatic than just 慌てる; suggests the kind of disorganized scrambling one does in genuine emergency or shock. A bit literary or formal in feel; common in narration but rare in casual speech, where you'd expect パニックになる or 慌てる alone.