The OA: 9 Crazy Fan Theories That Might Actually Be True
6. Or It's Actually True
On the other hand, perhaps Prairie really is telling the truth. After all, this is the way it's (mostly) presented during the show, and as viewers we're sucked into the story and led to believe what we're seeing actually happened.
The biggest of these is that she was definitely blind, did go missing for seven years (and was definitely in a New York subway station playing a violin at one stage), and then returned with her sight back. Even if other parts of her story are untrue, that's a fact - which could lend itself to the coping mechanism theory, but may also mean the rest of the story is true.
There's also the fact that she was adopted and, even if some of the Russian-set story is untrue, has ties to the country. Then there's the strong possibility she couldn't read English and the FBI planted the books; that she searches for Homer on YouTube before getting them (regardless of whether they were hers or planted); the whoosh noise; and had a vision/premonition (of some sort) of the school shooting.
None of it provides absolutely irrefutable evidence that her story is true, but added together it does all help point in that direction.