You really don't have to do anything about it besides omit it, since full-blown Sorcerers can live up to be 500 or 600 years old or more. Being 200 and still be young is not outside the realm of possibility. For all practical roleplay reasons nothing really changes for her. For the second, it's not a question of knowledge but really what the White Fellowship thinks of using Black Magic (which killing someone with magic usually is) they usually respond by beheading, even if said practitioner never knew about the Law. They're kinda old-fashioned like that. That said you are right that that would be solved if the robbers were killed at her house, since then it was in self-defense. 

By easier to heal I meant it'd be easier for her to bounce back from say a knife wound as a full-grown adult than as a child not faster. If you really want to go with that I'll let you do it but keep in mind that many villains won't pull punches just because Charlotte looks like a child. And it should bring up all kinds of in-universe issues with other characters but if that's how you want to do it then it's fine. 

Like I said it's not really an issue that makes the sheet problematic just an IC thing. And if the apprentices really are bad then she can probably go to the Fellowship for help but as she is not a member than there'll be some tension. 

Just fix those two issues and keep in mind what I said and you should be fine.