。
She poured water into the washbasin.
Literal
She [topic-は] washbasin [into-に] water [object-を] poured.
洗面器 (せんめんき) is a washbasin — literally 洗面 (face-washing) + 器 (vessel/container). 注ぐ (そそぐ) means 'to pour.' The に marks the destination where the water goes. A straightforward domestic-scene sentence with everyday vocabulary.