Not to take away from your main point at the end, but that's just not what discrimination means. Discrimination in this context isn't just making a decision between choices, it's when that decision is made unjustly or based on prejudice.
So yes, it's wrong to put profits ahead of people's well-being. But the question was whether insurance companies' policies to not pay out for causes of death that are strongly correlated with poor mental health unjustly treat people with mental health issues.
To be honest, I think that's an interesting point, because while I similarly find the whole concept of health and life insurance abhorrent, I think these policies are in place so people don't take their own lives for the sake of the insurance money for their loved ones. In that respect, they may save a handful of lives, and you could argue that makes it a just policy. I'm not sure I 100% buy that argument either, I just think there's more to the question than just whether insurance companies are generally moral.
Discrimination being tied to unjust, prejudiced, unfair, etc. treatment is part of all the dictionary definitions I found:
https://www.merriam-webster.com/dictionary/discrimination
https://www.britannica.com/dictionary/discrimination
https://dictionary.cambridge.org/us/dictionary/english/discrimination
https://www.oxfordreference.com/display/10.1093/oi/authority.20110803095721450
https://ahdictionary.com/word/search.html?q=discriminate