The thing with the Genie is that we get to see Regina genuinely… struggling with allowing him to take the fall, until the moment when he makes his terribly worded wish.
And then what we get is that beautiful, beautiful triumphant smile.
She can feel guilt about the Genie’s fate until the moment when he reveals his true colors and attempts to make her an object, just like every other person she’s going to war with. And for the first (and only?) time, the universe is on her side about it. He wants to look upon her face forever? Then he shall.
He violates her primary principle: a person is a person. And in doing so, he loses his own personhood—not through any action of hers, but in one of the few moments of actual justice in Regina’s life.