Say she had done what Sidney did during her first attack? Locked herself in her room? It was presumably upstairs, and we can see from the outside shots that her house lacks the sprawling, connected balconies that Sidney's house had, and therefore fewer ways in. When things started to get scary, but before she saw Steve and was therefore baited to stay down, she could've run upstairs and barricaded the door.

If she had done so, I wonder how things would've played out then. Ghostface may have tried to get in, but quite possibly wouldn't have had the time to do so, as they still needed to kill Steve, and her parents were coming. Maybe then try to kill the parents, but that might not necessarily have been doable. Maybe because of the element of surprise, maybe not because of numbers and the power of fighting for your child. Or maybe they would've just made do with killing Steve and leaving. They might've tried again the next night, but they'd then have their guard up, and Billy and Stu were on a schedule with their plan.

What's ironic is that right before Sidney's attack, she makes that comment about "running up the stairs when she should be going out the front door." Sidney ran up the stairs and survived. Casey went out the door and died, and if she'd gone upstairs, might have survived.

Thoughts?