I mean, I love this cute manga but....
Just forgiving an attempted murder does not happen. Sure, there may be circumstances that lessen the sentence, like in real life. But you don't get a "no punishment" verdict for attempted murder.
Also idk what's going on with the fiance. Didn't he ever know her? Did they not meet, ever? Plus he got super ntr'd.
To be honest, I would not just forgive the attempted murder in this situation. Be somewhat lenient, yes. But no punishment whatsoever, no.
And if I were the fiance, I might just leave. I don't think I could ever trust her after something like this...