I think, too, that sometimes it's the when the story is set that has a bearing on how names are spelled.
My daughter's name is Mariyah, but that name has always been spelled Mariah. I just like unusual spelling sometimes.
If Isidora was spelled like that at the time of the character's birth, then that's how the parents would've spelled it.
Nowadays, Michelle can be spelled Michelle or Michele. My parents were going to spell it Michele, but my grandmother said, "That's not how you spell it. It's Michelle." So...my name then became Michelle.