。
She put a spell on him.
Literal
She [topic-は] him [to-に] magic [object-を] applied.
魔法をかける ('cast a spell') is another かける idiom — extending the polysemous 'apply, put on' to magic. The recipient of the spell takes に. Used both literally in fantasy contexts and metaphorically (as in 'enchant, captivate' someone in a romantic sense).