Wait, if you fail the deception check then you can simply choose one of the other options? That's it? No penalty for trying to be greedy and deceive the hag??
As far as I'm aware, yes. Failing the deception you just get the option to take Mayrina, the Power or kill the Hag.
To be clear, if you try and fail to Deceive the Hag, then can you still attempt Intimidate her for both the power AND Mayrina? If you can't do this, then that's better than what I was thinking.
But I think there should still be some penalty for failing to deceive her. Maybe she no longer allows to choose Mayrina, or the power she gives you is slightly worse, or something. If you can roll a check for a better result, then failing that roll should have some consequence.