Unfortunately, I have (at the bedside of my late beloved father). And, you are right - there's no doubt. That's why this video caught my attention. If what we see on that video is for real - whether it's the "Lazarus effect" or whatever the reason - I can understand the mother not believing what the doctors are saying.
I don't know what the situation was like for your loved ones, nor what affect that would have on being able to observe the soul leaving the body.
I also don't know if any of Jahi's family were present at her death to witness the soul leaving the body, but I haven't read anything leading me to believe they were.