Yep, has to do with permissions, you're not the only one.
I'm not going to be supporting a Mac version, unfortunately, because I do not own a Mac and cannot test anything. Mac is not allowing Tailor Tales to write/overwrite files.
You can try locating the file joselina_avatar.png in game.app/contents/resources/app.nw/img/pictures/ and deleting it. It should get you past the intro, and you should be able to read the story, but you are unable to use the Outfit option - at least, that is my theory. No one has confirmed this yet.