I have no issue with any one who desires to box. I can see if impact would make the implant explode or leak then yes armor for that might be required but that to me defeats the idea of boxing.
Any pro sport has risks that if you have preexisting conditions you can not participate any longer, perhaps this is one of those cases.
What most boxing promoters try their best to avoid is death or coma. If that happens in a ring then it hurts boxing at all levels. As the organizers of matches I think they have the right to say who can / cannot enter into the ring at a professional level. If she wants to do her own thing well that is another issue.