Four weeks into her fast, Jean Davies, 86, told The Sunday Times: It is hell. I cant tell you how hard it is. You wouldnt decide this unless you thought your life was going to be so bad. It is intolerable.***
So I think what really happened is that she started with just stopping eating, and when that didn't produce her quick death, she realized she had to stop fluids also. At that point, the pain became so intense that she summoned her GP to give her something to alleviate her symptoms, ie. pain, and he gave her morphine for that, but he had to give her a small overdose so that she would stop breathing.
Ah, now it makes sense. She did get her assisted suicide after all hence the smile on the way out.