AFAIK The real problem with pedos is not the body of the child but mainly the mind. The lasting scars, mental traumas and the inability of the child to consent to such a thing are among the reason that make it much worse than other crimes. If she/he actually is 19 than she might be able to consent (I guess depending on the legal age of the country). I thus guess that from a legal stand point if she was able to demonstrate that she was actually an adult (if 19 is the case) and only the body changed, than they'd let her do it (if both are consenting, politically correct not withstanding and if there is not an additional reason that is not currently coming to my mind, obviously). If there was no magic involved and she was just a normal adult who really just looked like a child, she would still be considered as an adult everywhere. [ I was talking about the previews comments ]
Nonetheless this is pretty irrelevant as most people are here for the cuteness. I once heard that the sensibility to cute stuffs is there (evolutionally) to make sure humans would take care of their children instead of abandoning them, not other things.
I'd still add a spoiler tag to that description saying that she actually is 19, though. that description implies a wrong original age and that may drive many people away, as I nearly did.