even with zooming way in on it i swear it looks like a scar. maybe she cut herself somehow and it went unnoticed? It has the exact makeup of what a scar looks like on a dragon (to include, per that picture, a slight difference in the texture of the skin in that area). Black streaks dont just pop up. Its either a scar or it could be a fungus (though in my opinion it does not look like a fungus).