@Someguy
No one here is a good person, everyone is looking out for their self interest, but no one is evil for trying to survive.
What would happen if she fought earlier? The monster would still kill them all without a daily sacrifice, she would have to sacrifice him and continue the practice herself, or the rest of them would fight back against and sacrifice her instead. All she did was ensure she'd have more time to prepare for when she
would have to fight.