I don't think your distinction makes sense.

You're saying most mental health/suicide cases have hope, and thants probably true! But the article wasn't "every suicidal person granted euthanasia approval", it was approved for one very extreme case of mental suffering with no indication of improving. That would be like saying "most cases of pain still have hope". Yes exactly, they do, but there are rare, chronic cases where euthanasia may be a valid option, right? And just as much as suicidality is just 'a symptom of something' else, isn't pain also just a symptom of something else?

And obviously we should help suicidal people to improve their mental health, but in her case she has been struggling since childhood with no indication of improvement. So how was this "the wrong decision" for her?