@xxxNothingxxx
Because she has a house full of evidence that she did it?
Also, she might not have even bothered trying to frame him, because with all the evidence saying she did it, the only way out would be to claim you are being framed.
Considering its
a whole greenhouse full of the stuff inside her house, it's not very likely anyone would even belive that even if it was a present who accused her.
Also what benefit does killing her give to the MC.
If anything it would make his relationship with the king worse.
Sure he might have been able to get away with it claiming self-defence or even hide all evidence that he did it.
But again, it doesn't benefit him in any way.
And IF he went with the "remove the evidence ", if it ever came out that he did it because of magic or whatever, it would make him look even worse for hiding it.
The only "benefit" killing her would be that it removes a potential threat, but considering she is locked up by the king himself it's not very likely she is going to get out anytime soon.
And the minor risk of her doing so is not worth souring his relationship with the kingdom.