For the most part I like it but I have a few issues. 

The idea that Charlotte stopped the aging process completely is problematic. Things like Immortality are still pretty much outside the realm of possibility for most mortal magic-users, but that said they do tend to have longer life-spans than normal humans. So she could be in her twenties for a long time but she can't stop the effects of aging entirely. Stopping the aging process entirely would require a continuous source of massive energy that you can't really get without resorting to Black Magic in most cases and even then it's a wash. For all practical purposes nothing changes but it's a continuity thing.

And when she killed her father's killers out of revenge with her magic that's going to be a problem for her because of the White Fellowship of Sorcerers and their Laws of Magic. One of them explicitly forbids killing mortal humans with magic when not defending themselves or another from imminent danger so that piece needs to be tweaked. If the law wasn't their then there would just be Sorcerers running around killing whoever they wanted willy-nilly. This one can't really be on you because I have yet to write that into the Codex but it's there. 

Regressing herself to a child is dubious logic at best. Easier to heal? Maybe but there are all kinds of drawbacks. The body is much weaker and easier to injure in the first place and any kind of protracted highly athletic activity, such as every mission up until now, would take a huge toll on someone with the body of a child. Her adult body would have more natural energy and athleticism and heal easier naturally and besides that garner more respect from people she meets. It all seems like an excuse to play a loli, and I'd rather you take out the whole thing but I want to hear your thoughts on this.

And on a completely unrelated note, I have to shake my head at Charlotte's logic for being surprised her apprentices turned out to be Warlocks. It's like teaching somebody to cook meth and make bombs and not expect them to turn out to be criminals. It's not a character sheet killing flaw but in-universe it kinda makes her look dumb.