You're quite welcome.
I made it clear to the young woman (who was planning to dive alone), that I would help her out, but I was not going to change my own dive plan significantly to accommodate her. I dive perhaps a half dozen times per summer in the NorthEast, the dives aren't cheap, and there's no way I'm going to cut a dive short just because a newbie pulls a bonehead move and lets go of a wreck reel line.
Now there are some, perhaps many who might say "you've taken responsibility for this diver by offering to dive with her, and when you looked back and saw she was not on the reel line you should have immediately ended your dive!" Or as you suggested "Look behind you every few seconds to make sure she's still on the line".
And perhaps, from an "ethical", "proper dive etiquette", "safety" point of view, they'd be right.
As far as I'm concerned, this diver, who planned to jump in alone, with no reel, with no redundant gas supply, was better off having me as a guide, at least up until the point she decided to let go of the line and do a free ascent.
My girlfriend was recently certified and during her post OW certification dives in the Caribbean, my eyes were on her the entire dive. She's planning on giving the NorthEast diving a try in a few months, and I will do the same thing on those dives.
That's not the same situation as the incident I mentioned on this thread, as far as I'm concerned.