I and many others would be thoroughly pissed if that happened. The only reason Karina isn't dead right now is pure luck.
In 999 out of 1000 realities, she would be dead. Aurora must pay for the near-certainty of death for her sister. NGL, the only solution that makes sense is killing Aurora and arranging her body to make it appear to be an accident.
Harsh? Yeah, but even if Aurora didn't want Karina killed, she's responsible for letting the order get through, especially given how obsessed the prince seems with her.