。
She despised the boy.
Literal
She [topic-は] that boy [object-を] despised.
軽蔑する ('to despise, look down on') is a strong verb of contempt — much heavier than 嫌う ('to dislike'). It implies moral judgment, not just personal preference. The kanji 軽 ('light, slight') + 蔑 ('disregard, scorn') paint the image of treating someone as beneath consideration. In everyday speech you'd more often hear 馬鹿にする ('make a fool of') or 嫌う; 軽蔑する belongs more to literary narration or formal commentary.