。
She deposited a large sum at the bank.
Literal
She [topic-は] large-money [object-を] bank [at-に] deposited.
預ける ('to entrust, deposit, leave in someone's keeping') is the standard verb for depositing money, leaving luggage at a left-baggage office, or putting a child in daycare — anything left in someone else's care. に marks the recipient/keeper. 大金 ('a large sum of money') literally 'big money' is a fixed compound; ordinary amounts would be 大きなお金 (less idiomatic) or just specific figures.