。
She arrived at the station at seven o'clock.
Literal
She [topic-は] seven-o'clock [at-に] station [at-に] arrived.
七時に (at 7 o'clock) and 駅に (at the station) both use に — the first for the time point, the second for the arrival destination. 着いた (arrived) is the past of 着く. The double に is natural in Japanese when both time and place are specified with the same particle. A clean, basic sentence for practicing time and location expressions.