Wicked
Evil
な adjective
The kanji and the word are exactly the same. That means they share meanings as well.
This is a long reading for such a short word! Think of something being wicked. Evil, even! But what is wicked? It's the side of the island... but only the side. It's the 横島 (よこしま).
神様は私の邪な心を見透かしていらっしゃったんだわ。
God saw through my wicked heart.