This is very tricky, as it must be one of the most painful experiences that anyone can go through to have a loved one take their own life. So feelings will be running high, so a choice of words can cause a response in someone who is grieving , and they react in a way that they wouldn't react to in other circumstances.
I remember that when my FIL died in a car accident, my DH reacted strongly when I was telling family members what had happened; I said that his dad had been 'killed in a car accident', and he found it a very hard expression to hear.
It's the pain that's talking, so if someone reacts angrily at a time of intense grief, it shouldn't be taken personally, but also take on board what they're saying and don't use terms that they've told you they find upsetting. (If you're the one who's coping with the loss, then you should feel free to use the terms that you want to use, of course.)
I also think this causes strong feelings because of the fact that committing suicide used to be seen as a criminal act, but more so, I think, because the RC church used to see it as a mortal sin and it led to people not being buried in concentrated ground if they had taken their own life.
This was so wrong, because no one commits suicide apart from when under extreme distress and, mostly, when they're not in their right mind , (apart from when a very ill person wants to die with dignity when terminally ill).