。
She gazed steadily at her child's face.
Literal
She [topic-は] her own child's face [object-を] fixedly looked.
じっと is a 擬態語 (state mimetic) for stillness and intent focus — じっと見る ('to gaze fixedly, stare') is a stock collocation. Distinct from 凝視する (formal 'stare intently') and 見つめる ('gaze at'): じっと emphasizes the stillness of the looking, the absence of motion. Pictures a parent absorbing their child's features in unbroken regard.