。
She took care of her son.
Literal
She [topic-は] son [genitive-の] looking-after [object-を] saw.
面倒をみる is a fixed idiom literally 'look at the trouble,' meaning 'take care of, look after.' 面倒 ('trouble, bother, care') paired with 見る ('look') gives the caretaking sense. Used for caring for children, the elderly, the sick, or even for arrangements. 面倒 itself can be a na-adjective meaning 'troublesome' or a noun for 'care/attention'; in this idiom it's the noun reading.