。
She looks after my child for me.
Literal
She [topic-は] my child [possessive-の] care [object-を] do [for-me-てくれる].
Another common variation: instead of 子供を, this uses 子供の世話 ('the care of the child') as a noun phrase, then makes that the object of する with を. The two forms 子供の世話をする and 子供を世話する are interchangeable in meaning; the の version treats 'child-care' as a unified concept, the を version treats the child as the direct object of caring. Both are natural.