。
She held the child tight to her chest.
Literal
She [topic-は] chest [to-に] child [object-を] embraced-tight.
抱きしめる is a compound verb that intensifies the embrace: 抱く ('hold, embrace') + 締める ('tighten, fasten') = 'to clutch, hold tight, hug close.' The に on 胸 marks the destination of the holding — 'to her chest.' The image is physical and emotional at once: pulling a child close to one's chest is the gesture of protection and tenderness, common across cultures but compactly expressed by this verb.