Demoting them to commoner might not be a good idea because they could always come back, it's better to exile them. The second one probably won't happen because she won't try to save her father or sister because of how they've treated her. I also doubt an entire castle would catch on fire, most parts of it would catch fire. Plus being raided by demons doesn't seem likely since the ancient god or whatever can do his god thing and boom boom boom the demons fail or something like that.
take my third option too
Selena the princess is casted magic the the ancient god to be all men's lust, aka biss in heat while the father is becoming crippled and make all his bad behaviour be in public and lost his king status also the servants met their ends one by one, our fl can be the queen with the god as her partner uwuu ヾ(❀╹◡╹)ノ~
So I’m thinking two ways
1. She becomes Queen and takes away the the title “king” and “ princess” from her father and sister , then demote them to commoner so that they lose their power and glory.
Or
2. “Accidentally” the castle catches on fire or is raided by demons and the king and princess die but she stays alive and acts like she tried to save her sister and father but in reality she let them perish.
Give me your thoughts on this ヾ(❀╹◡╹)ノ~