I had a close friend who told me he was going to do it, but it might be in 5 days, 5 months, or 5 years, so I couldn't call the authorities on him to get him help. He had tried a couple of times without success so I knew he was serious. I just told him I wasn't ready to let him go, and remained his friend, although we rarely talked about it. Unfortunately, when he was ready, he didn't reach out and was successful. That was in 2007. Deep down, I knew there was little any of us could have done to prevent it.
You did well with Nancy and made an impact when she needed you. As you know, suicidal ideation is frightening. I'm sure you played a large part in her being here as you listened when she needed you most.