Being the prince of sneakiness and murder makes you good..?
Boethiah is the prince of deceit, conspiracy, secret plots of murder, assassination, treason and unlawful overthrow of authority, so no, I would not say that Boethiah is any good..
But when it comes to Daedric Princes, there really is no "Good or evil".
That's only part of her sphere. Boethiah is a patron of wolves, not lambs. She has no interest in the poor and downtrodden, and if you let yourself get murdered or overthrown, you didn't deserve to rule.
Revolution and the overthrow of illegitimate rule are the flip side to her coin. Think of the American, French, or Bolshevik Revolutions, or the plot of Dishonored for a fictional example, all of which involved conspiracy, murder, and the unlawful overthrow of authority.
It's all a matter of perspective.