i prevented the sister from getting smashed by talking to her and leaving the dialog open until the music changed. it wasn't until later i figured out what i was supposed to do to save her from the chandellier.

I found a pretty crazy bug, if you speak to mum very quickly in succession while she is passing the shelves and you are to the left of her, she starts moving towards the door without any animation, and then spends the entire rest of the game just going through the door over and over very quickly. (some parts of the video are sped up when nothing is happening)

She doesn't die, get possessed, try to kill you, or make sandwiches at any point. You can kill her with the axe if you do it while standing in the kitchen, as she is not in the hallway for long enough to hit her.

You can still talk to other characters as usual, but the blank dialogue box is still there after they finish talking to you.

When Dad arrives, she slowly phases off of the screen before returning to go in and out of the door again as you bleed on the ground.

I've been able to replicate this very consistently, as you can see it only took a few conversations for it to work, but it only seems to work when standing to the left of her and in this specific area. It works regardless of any items you are carrying/what you are holding while you speak to her.

It doesn't seem to happen to any other characters, or in any other rooms with her.