It is in the best interest of everybody to offer assisted suicide at a set time and date instead of taking the matter into their own hands and leaving family, friends and first responders with the trauma of discovering a body.
Except they certainly haven't, both because of very limited resources and became they are probably in no condition to figure what they could or should try themselves and are dependent on doctors, family members and other people (who also might have only very limited capacity to help her)
What's the limiting principle here exactly? If we normalize the idea that suicide is a solution to any problem, it's inevitably going to start being used as a "solution" for more and more problems: treatable illness, poverty, old age, disability, dependence on those who'd rather not shoulder the burden of caring for you.
It's already happening.
What I say is that, for those cases where professionals have reasonable suspicion that it would happen anyway, offering a more humane option is the right thing to do. It shouldn't be an option to be offered lightly to anyone.
For example, here's the story of a disabled Canadian man who "consented" to euthanasia because he thought it was his only alternative to homelessness:
https://www.independent.co.uk/news/world/americas/canada-eut...
In this case he withdrew his "consent" after strangers helped him out financially, but I'm sure there are other cases that didn't end so luckily.
As suicide gets normalised you can expect the concept of "consent" to get expanded even further beyond the bounds of decency.
The edge-case is that the person wants to become an early suspended customer of a cryonics organization. Already there have been successful suicides from people who stated they would have preferred to be suspended and have the very small chance of actually getting a second chance at some distant point in the future, but there are various legal obstacles as well as practical ones to that, and so these people are just as assuredly gone forever as anyone else.
Besides being complex, it's also an old issue. You might enjoy reading this case report from 1993 about a suicidal person who wanted to be cryopreserved: https://www.cryonicsarchive.org/library/complete-list-of-alc... He did eventually shoot himself, and unlike others there was at least a brain preservation in the end, but it's pretty far from an ideal one (and no one knows if even ideal preservation is good enough for future reanimation/emulation; I'd bet against it but obviously wouldn't rule it out). More recently, in late 2018 the first person was cryopreserved while using California's new end of life option act to hasten an otherwise painful demise from stage 4 cancer. (Short version: https://www.cryonicsarchive.org/library/complete-list-of-alc... Long version: https://www.cryonicsarchive.org/docs/alcor-case-report-a-199...)