In a fit of anger, she broke off the engagement.

Literal

She [topic-は] anger-driven [adverbial-に] engagement [object-を] broke.

腹立ちまぎれに ('in a fit of anger') — まぎれ means 'caught up in, driven by,' attached to an emotion noun. 婚約を破棄する ('to break off an engagement') uses formal Sino-Japanese vocabulary.