It can sure be a bit unsettling to have a life pass unexpectedly in front of you. I've had a good number of people pass while I am at work. I have said a prayer for each that has passed and those that were in critical condition.
There may be a few factors that can help a persons chance of survival...and it all starts with early CPR. What a nice thought it could be if we were all afforded the chance this young lady had with you standing there.
Everyone could take away a different message from one given situation...and that's really fine. We're all in a different place in life. On a cloudy rainy day with nothing to look forward to... look at some clouds, or a tree, or a child's smile. On even the worst day out there I look at my boys sad face and ask him if there were ever a better day to be alive.
There is much to be thankful for in life...and with that there is much to be thankful for in death. It's not easy, it's seldom ever easy. But look at the way a perfect stranger has effected your life, and you hers (and her family). You cared enough to do something that you felt was the right thing. My prayers are also with you.
We do affect other people, even those that we don't know. Hug your family members, smile at a stranger, bring a shopping cart to the corral for someone on the way into a store. That person standing next to you might just need a smile from someone, they could have just lost a family member.