Hi

Whether your friend is controlling her diabetes by pills, diet or insulin...all you can really do imho is tell her how dangerous it is for her to eat so much chocolate in one go. You can remind her how it sends her blood-sugar levels out of control, and gently remind her that diabetes is a serious condition. Perhaps you could also find a gentle way to remind her that diabetes can also be fatal if ignored.

Good luck in helping her.

and to you.