I doubt that the Chantix is to blame. She was no doubt close to the edge in any case. You should put the responsibility where it belongs, on her.
But what's bad for the other smoking-cessation products is good for us
Chantix is well-known to have a side effect that produces suicidal ideation in people that never considered it otherwise and did not suffer from mental illness and the rates go much higher on individuals that have had past mental health issues. It is a well-documented side effect and the death rate related to Chantix suicide and the other antidepressants that are used to help people quit smoking is much higher than the current lung illness death rate which of course we know is not related to nicotine
vaping but still. When I was seeking a doctor's assistance to quit smoking this is one of the reasons he told me he does not prescribe what amounts to antidepressants to people who aren't depressed simply because they smoke cigarettes. It's really not that far-fetched if you think about it this is an antidepressant used to change the chemical makeup in the brain and when used for a person who is depressed that is an appropriate thing to do but if a person is not depressed changing the chemicals of the brain can have some very bad side effects including creating a near psychotic state in which a person may feel like they need to die. If you go to the page you'll see it listed as a side effect