For alternate starting points/origins:
-the sci-fi one above but without the transformation part; she already knows what she is, and she already looks like it, and perhaps simply have used some form of hologram while growing up on Earth.
Or one where it's far enough into the future she could grow up has a hybrid on Earth and while that was Weird, people knew about aliens so it wasn't any cause for actual alarm.
-actual fantasy (of the 'medieval setting', elves and orcs kind) where she's either a literal half-unicorn or was turned into one by a mage for some reason, as far as that worked.
-modern fantasy in contrast to the urban one, but she'd be a literal half-unicorn in this case.
-the sci-fi one above but without the transformation part; she already knows what she is, and she already looks like it, and perhaps simply have used some form of hologram while growing up on Earth.
Or one where it's far enough into the future she could grow up has a hybrid on Earth and while that was Weird, people knew about aliens so it wasn't any cause for actual alarm.
-actual fantasy (of the 'medieval setting', elves and orcs kind) where she's either a literal half-unicorn or was turned into one by a mage for some reason, as far as that worked.
-modern fantasy in contrast to the urban one, but she'd be a literal half-unicorn in this case.