I too have a lot of theories about the ending, and I like to imagine that not even the writers consciously know the full plot of their creations or have absolute control over them.
Since I've heard these crazy stories about how people react when meeting their doppelgängers, I wanted to give it a sci-fi touch. Also, for those that like to go beyond and explore the nooks and turns of the human mind, there's also a possibility that the author of the letter was suffering from schizophrenia and imagined it all. Or maybe Vero89 is another personality of the patient. DID can be a fascinating subject too. Either way, she ended on Soteria, a mental facility.
I'm glad you liked the story <3