Staying on the subject communicates several things to the suicidal person. It says you care. It says you're not afraid of their feelings. It says you take them seriously. Most of us have considered suicide at one time or another in our lives.
People are suicidal only for a limited period of time.
In the vast majority of cases, things get better with time. Usually something changed. Whether it's the person's view of the situation or the problem itself is resolved, something has to give. All kinds of people commit suicide, including people who are depressed due to biochemical factors that have nothing to do with love. More adolescent suicides occur in the morning before school or around dinner time.