。
She gently caressed the baby.
Literal
She [topic-は] baby [object-を] gently caressed.
愛撫する (あいぶする) means 'to caress' or 'to stroke tenderly' — a somewhat literary word composed of 愛 (love) + 撫 (stroke/pat). 優しく (やさしく) means 'gently' or 'tenderly,' the adverbial form of 優しい. The combination paints a tender, nurturing scene.