The OA: 9 Crazy Fan Theories That Might Actually Be True
2. Rachel Was A FBI Plant
The idea that the FBI have been heavily-involved in the tests around the 'angels' is an intriguing one, and certainly the notion of Elias planting the books in Prairie's room holds a fair bit of water.
Even more evidence comes from the braille on a wall at the offices where he works, which it's been spotted reads the word 'Rachel' (or at least R1C85L, but it does fit).
Curiously, Rachel was the only one of the captives to not receive a movement. Why would this be, when all the other captives did? Because she's not an angel, and thus never supposed to receive them. Instead, she's an FBI plant, put there to learn the secrets of what was going on and pass them back to the agency, although she may or may not actually be a NDE survivor.
There's also a suggestion Hap is in on it too. It's probably more compelling if he isn't, and Rachel is a mole even he doesn't know about, but it could work if he needed someone to really gain their trust in a way he couldn't.