This was really interesting. I like the unreliable narrator aspect of it, how the lack of close-up visual details means we can only really go off of the things Laynie says to understand what is happening, and since we're presented with a choice of different contradictory explanations for everything, we can't trust that either.
I initially leaned more toward the weirder, more fantastical choices, but I eventually started gravitating to the grounded explanations: stories about domestic abuse or childhood injuries. My final outcome the first time was the one about Johann, and on my second playthrough Laynie accepted that the skeleton was hers.
My initial interpretation was that she was abused by Johann and turned to self-harm to replace the injuries he gave her with self-inflicted ones, while justifying it with the more fantastical explanations, but not all of her injuries or other findings seemed to originate from the abuse, plus she still ended up concluding that her skeleton was not her own. At this point, I think there's a chance that some of her stories about childhood accidents or abuse might be true, but that most of the things she finds are the result of previous self-harm. Of course, even though Laynie accepting that the skeleton is hers feels the most like a "true ending", everything is presented in such ambiguous terms that I can't really say if there is a definitive, canonical truth to be found here.