Those who haven't encountered true persistent depression have no idea what it feels like to be incapable of feeling any kind of joy. In her case she also had constant panic attacks and was unable to function in society.
Is it really living if your entire "life" consists of going in and out of mental hospitals and never being able to sustain a normal relationship or conversations with any other human?
Article says two doctors confirmed it. This wasn't just something that popped in her head one day.
Also, why would someone's academic qualifications entitle them to essentially sentence a suicidal person to death?
[1]: e.g "Also, if by some chance a psychiatrist doesn’t give a patient Adderall, that patient practically always goes to another psychiatrist, and that next psychiatrist does." (https://slatestarcodex.com/2017/12/28/adderall-risks-much-mo...)
Your argument goes both ways then, both for those who are pro-euthanasia and those who completely are against it.