Thanks Sunflower, it is harder, and hard not to feel some guilt that you could have done something to prevent it. Even if you know intellectually there wasn't. My father spent the rest of his life alternating between trying to find people to blame (himself and my brothers and I included) and denying it really was suicide as opposed to an accident or murder. There was no talking to him about it.
My take away from the experience is that anyone contemplating suicide needs to think about the impact it will have on others. I know that may seem impossible in that frame of mind, but if they could it might stop some people. Anyway this happened to us 10 years or so ago and most of us have moved on for the most part, I hope your husband has. Your mother in law may never be able to completely do that.