I've been close to the edge myself. I never thought about suicide seriously, though. It did cross my mind. But my depression was due to my situation and not due to any inherited imbalance. My kids are disabled with autism and that is what was driving me nuts. They still have their disability but several things have changed that have mitigated my mental state.
My kids are a bit more mature (every little bit counts) and I am taking better care of myself (exercising daily and taking time to do music). I can't imagine having the notion to kill my kids for months and not confiding in my husband.... I just plain don't understand being that far out. I really have no sympathy for her.