。
She entrusted the child to her aunt's care.
Literal
She [topic-は] child [object-を] aunt [genitive-の] care [to-に] entrusted.
委ねる ('to entrust, delegate') is a heavier, more formal verb than 預ける ('to leave with, deposit') — entrusting a child here implies real responsibility transfer rather than overnight babysitting. The kanji 叔母 specifically denotes a younger aunt (a parent's younger sister); the older counterpart is 伯母, both pronounced おば. Japanese kinship terms encode relative age this way for siblings of parents (叔父/伯父 too) — a distinction English flattens into 'aunt' or 'uncle' regardless of age order.