[Discussion] Anime-Only Theory: Rui Arneb is Behind Everything Happening in Episodes 8 & 9

I think the events of Episodes 8 and 9 are being orchestrated by Rui Arneb (Gluttony - Satiety).
The first clue comes all the way back at the end of Season 3. When Sirius is captured, she warns Subaru to beware of the Gourmet, Bizarre Eater, and Satiety because they will try to take everything from him. That warning feels incredibly specific in hindsight. Shortly afterward, Subaru loses his memories, his identity is questioned, and chaos breaks out around him. It almost sounds as if Sirius already knew what was going to happen, possibly through her Gospel.
The biggest piece of evidence is Subaru's memory loss. So far, the only characters known to steal or manipulate memories are the Gluttony Archbishops. When Subaru suddenly wakes up without memories in the Pleiades Watchtower, Gluttony immediately becomes the most likely suspect.
The main issue with this theory is that Shaula should have killed any Archbishop approaching the tower. However, I think Rui may have bypassed this by possessing Rem. Unlike the other Gluttony siblings, Rui has shown abilities related to souls and consciousness. If she entered Rem's body after the events of Priestella, she could have reached the tower without triggering Shaula's defenses.
This would also explain several strange moments. During Subaru's loops, Rem and Shaula appear with injuries that remind me of the wounds Otto suffered when Rui attacked him in Season 3. More importantly, when Rem kills Subaru, her voice sounds different and she says:

"Try to guess better next time, my hero."

"My hero" is a phrase strongly associated with Rem, but the delivery feels off. It almost sounds like someone using Rem's memories rather than Rem herself. Since Rui can access memories, this would make sense.
I also think Rui is responsible for the incidents involving the staircase. Rather than simply killing Subaru, she seems to be forcing him into repeated loops and increasing his paranoia.
The biggest clue comes at the end of Episode 9. Subaru briefly loses consciousness while talking to Meili. When he wakes up, Meili is dead. Everything points toward Subaru being the killer: strangulation marks, blood under his nails, scratches on his hands, and the message "Subaru was here" written on Meili's body.
But the scene feels too perfect. It looks more like a setup than a genuine murder. My theory is that Rui temporarily took control of Subaru's body during his blackout and killed Meili herself.
The question is: why?
I don't think Rui's goal is simply to kill people. I think she's trying to destroy Subaru's identity. Arc 6 constantly asks the question:

"Who is Natsuki Subaru?"

By stealing his memories, making him suspect himself of murder, turning others against him, and isolating him from people who trust him, Rui is attacking the very foundation of who Subaru is.
Meili's death also supports this. She was one of the people most likely to help Subaru understand who he used to be. Removing her isolates him even further.
So my current theory is that Rui infiltrated the tower through Rem, stole Subaru's memories, manipulated events from the shadows, temporarily possessed Subaru during key moments, and is now trying to completely break his sense of self.
What do you guys think? Am I missing anything that supports or contradicts this theory?
(Anime-only discussion please, no Light Novel spoilers.)