There is always hope, this is what it is to be human even at your darkest hour there is hope.
She was 17 for god's sake, not fully developed mentally as an adult. At that age people make so much mistakes, they should not be allowed to make this fatal mistake.
So how long do you propose they should have tied her down, and force fed her against her will?
5 years?
10 years?
25 years?
As that's what it would effectively have taken and even if she ever appeared to have changed her mind, how do you know that the moment she was given a couple of minutes alone she wouldn't have used another method? (run in front of a bus on a court visit, jumped off a balcony, cut her wrists with broken glass the list is almost endless).
She wasn't someone taking pills or jumping off a bridge on the spur of the moment, she was sadly someone who had obviously had treatment for years but still felt the same way and the only way to stop her would have involved a complete deprivation of liberty bodily autonomy (worse than almost all criminals) potentially for the rest of her life in which time she would still be suffering, which is to put it bluntly pretty ******* inhumane.
She was someone who was clear in her mind what she wanted, able to argue for it, and in the end took a very slow way to do it when other options were denied her and the only way left was to refuse to allow things into her body.
I believe in trying to save people when possible and if possible prolong life, but not at all costs and not when the person is lucid enough to make their wishes clear and any other option would be against their will and effectively torture.
You appear to have a very simplistic view that life should be preserved regardless of the persons long term and argued for wishes and suffering.