[quote=@Lugubrious]
Law of Retrogression – transforms the target into a younger version of themselves.  The exact age depends upon the person.  Often this curse will 'lock' onto an age during which the target had a significant experience.  This transformation may awaken earlier memories or restore forgotten abilities.  Typically, the target is weakened both magically and physically, though this isn't always the case.  This curse can last up to two days if Nero wills it, but cannot be permanent.  Clothing is altered to fit the new body.
[/quote]

Based on this shouldn't I be deciding the age that she regresses to?

Since the age she is now is before her magic was discovered would she still have it? Bear in mind she always had her magic it just wasn't till she was ten that an event forced it out of her. Does her personality regress with the bodily changes or is it just a physically and magically decreased?