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She gave up the plan against her own wishes.
Literal
She [topic-は] her own intent [against-に反して] plan [object-を] gave-up.
~に反して ('against, contrary to') marks something running counter to a stated frame — 反する literally 'oppose, contradict.' Common in formal Japanese for 'against expectations,' 'against orders,' 'against one's wishes.' 断念する ('to give up on, to relinquish') is the formal verb for abandoning a plan or hope after deliberation — distinct from 諦める ('give up, resign oneself,' more emotional). The phrasing fits a reluctant, externally pressured concession rather than free choice.