A: First and most important, you should be seeing a therapist who specializes in Dissociative Identity Disorder. You need that support and direct help to marshal the other alters to manage the depressed one. Your internal group can protect the desperate one and, not incidentally, protect the rest of you, just as a group of good friends can gather around to support someone in the world.
I wish you well.
Hartwell-Walker, D. (2008). Suicidal Alter. Psych Central. Retrieved on October 17, 2017, from https://psychcentral.com/ask-the-therapist/2008/06/20/suicidal-alter/