I do not have the answers.
All I can offer are some observations. Some of these may pertain your situation, others may not. If you are looking for expert advice, good luck. If you find it, please share it with all of us.
Observation 1: All suicides are different. I know that sounds like a cop-out but each individual is born with a different genetic structure and matures within a different environment. Just like it is not reasonable to predict “Jim” will commit suicide because his uncle “Bob” did, it is not reasonable to expect that all children with permissive (or strict) parents will commit suicide.
Observation 2: The suicide was not the fault of the survivors. As a parent this one was very hard to realize. But it ties in with observation 1. Let us suppose that I was the worst parent in the world. That I belittled my son, that I beat him, that I abused him. I am sure that you have read newspaper articles about such parents. Some have even locked their child in a closet for years. But even under those extreme conditions, the child did not commit suicide. That is why I know that it is not what someone says or does that forces someone to commit suicide.
Observation 3: Suicide is not the result of what happened immediately before. It is a culmination of many things happening over a relatively long period of time. Most of these things would seem insignificant to the average person, but seem insurmountable to the person who committed suicide. That's why you hear the phrase, "Suicide is a permanent 'solution' to a temporary situation".
Observation 4: Once a person decides on suicide, nothing that you say, nothing that you do will prevent it. You might be lucky enough to delay the process for a period of time, but without the person making a life-changing realization that his or her entire perception of the world is "askew", you are only delaying the inevitable. In fact the person may begin to hate you for stopping them.
Observation 5: If you do not believe in life after death. Fine. Then their suffering is over. That is exactly what they wanted. We are the ones that are left behind to suffer, and to wonder, and to feel guilty, etc. Everyone dies sooner or later and they were able to choose when and how they would die. One of the greatest fears anyone has is not knowing when or how he or she is going to die. The person who commits suicide takes that fear out of the equation. I'm not saying that it is right, only that they feel they have gained control over the situation.
Observation 6: If you do believe in life after death. Fine. Then the suffering is over. Then you can also believe that they are in a better place, however you define that. Work towards the day that you will visit with them again. You might want to "slap them upside their head" for being to "stupid". You might want to tell them how much you have suffered from their suicide. However you feel, write it down...memorize it...you can give them your speech when you get there.
Observation 7: You have knowledge about the person that no one else has. Others may only know of their final act. Still others may have known them only casually. You can extend their memory, in effect extend their life, by sharing what you know with everyone who will listen. I have often heard the saying, "They are not really gone as long as they are alive in our hearts."