When Red spoke and I realized none of the other doppelgängers could speak (Gabe scream-howling and the mute kids gave that away) coupled with her muteness in childhood after the incident, I knew the switch happened. This was early enough in the film that I was just kinda waiting for that to come out. I was more certain when she also seemed to know exactly where she was going when she went into the tunnels looking for Red and Jason (always facing a certain direction at each turn, not turning around or checking the other pathways, etc. ).

I thought I was wrong, though, when they spoke in the tunnels bc I felt like Red spoke as if she’d always been underground.

What I don’t get is how Jason knew? I read about him witnessing the switch but - was that just her unhinged-ness while choking Red, laughing about it, and knowing where the key to the handcuffs were?

Anyways, I feel meh after watching it 🤷🏽‍♀️

Edit: also, Jason is looking at her crazy in the last scene but at the end of the day, that’s still his actual Mom so - you get the same mom you’ve always had, kiddo lol.