Yaaa that video would be nothing more than her treating the YouTuber horribly. I’m assuming the cat is either a cat they both know and she ended up taking care of it for her after she stopped going to school or the cat is insurance as well as a boost to views to make her look more wholesome. Either way I hope the sister gets out of that room, it seems her sister is part of her unstable mindset and causing identity crisis.
As for Mc, just give up from this point on and run. She will beat them all up anyways with or without you.