Yeah, this is pretty much how it would go if the prince broke his engagement in such a dumb way, and with a "fake villainess" (meaning innocent of the ridiculous accusations) of high status in place of a commoner or similarly weak "heroine". Honestly, if you're not framing her for treason at the very least, you shouldn't even bother. I liked the touch of the nobility getting behind her when the prince suggested capital punishment and was "talked down" to lifetime imprisonment. Again, that's the obvious response to an insane tyrant in the making.