So why aren’t they just framing her for a ridiculous crime she definitely didn’t commit but she can’t prove? You’re giving yourself an unnecessarily hard time
Why would she be convicted of any crime when she is the law? I mean, she's the hear to the throne, as her father's will has unmistakably stated.
Moreover, she's always guarded so it's basically impossible for her to not have an alibi.
The real silly thing is that these two fools assassinated the king, but didn't have any plan regarding the will (to create a forgery and ensure that they be named heir) nor apparently have any faction supporting them. I mean, there's no politics here; the people we've seen in the castle are all very loyal to the king and his daughter, and all the schemes of the stepsister and stepbrother are discussed exclusively between themselves while wearing masks. They're seen only hiring external help (who are non human) or servants and don't appear to have tried to set up some coup with the people actually running the country (the daughter is clearly clueless about how that works and doesn't seem to do all that much besides eat and sleep).
I wonder how they escalate from this though. They're already hiring people they would be unable to pay unless they got the throne. I guess in this case they won't need to pay because the assassination will have failed and maybe all the assassins will have died.
It's pretty crazy that these guys are just coming up and entering the castle while wearing masks, silly clothes and swords. What are the guards doing?