The believer that commits suicide is mentally unbalanced, for whatever reason. It probably has nothing to do with whether they trust in Christ... when they reach that point, they are not in their right mind. Does God send mentally disturbed people to Hell?
That is not always true. Some people just can't handle whatever they are facing in life and just want to get out of it and suicide is their escape, so they think. Most unbelievers commit suicide because they think that the are just going to cease to exist. And once they commit that act, they unfortunately find out the real truth, which is that their spirit will just depart from the body and go to their respective places.
My point in all of this has been that, I would not put any stock in one who claims to be in Christ but commits suicide as being safe. As I said, we don't know how God is going to treat that. And if a believer were to commit suicide and find himself in Hades, there are no do overs, no finger pointing and no one to take your complaint to.
We are saved by grace through faith. Not a one time confession of faith, but faith from first to last. What we do know is, suicide is murder and it is not of faith.