。
She broke the window on purpose.
Literal
She [topic-は] intentionally window [object-を] broke.
故意に ('intentionally, deliberately, on purpose') is a stark adverb — used in legal and journalistic contexts to mark mens rea, the deliberate intent. The Sino-Japanese compound 故意 ('intent, purpose') derives from 故 ('cause, reason') + 意 ('intent'). Compare わざと ('deliberately,' more colloquial) and うっかり ('inadvertently, by accident'). The choice of 故意 elevates the register, suggesting a serious or considered action — fitting for breaking something deliberately rather than by accident.