Do you believe that only mentally ill people commit suicide?

[Cinjin]

I think that anyone would kill themselves if things got bad enough, it's just that everyone has different tolerance levels. There are people who have gone through what she has gone through and didn't end their lives, some got back on their feet, some became homeless.... So does that mean she had a mental illness??

No, but technically you can't really rule that possibility out.
That being said, I've heard that many people consider suicide at least once in their life, even if it was only for a brief moment. Life sucks sometimes, and we all look for a way out of shitty circumstances. I wouldn't think for a moment that one has to be mentally impaired to eat a bullet. I do however think that they absolutely must be completely overwhelmed with what may very well be an impossible situation.