I've been wondering myself if the fact that she was an avid photographer had skewed her view on the buddy system. It sounds like she had a habit of drifting away from her buddies. Question is why someone would develop such a habit.
From what I've seen and read on the forum, I believe divers' views of the buddy system are widely divergent.
One of the philosophies put forth in solo diver training is that if you are not diving with a capable/competent, attentive buddy, you are, for practical purposes, diving solo. I disagree in the literal sense, but consider there to be some truth in this. And an example given is an instructor working with students, whom he supposedly can't rely on in an emergency (that actually depends on the student, training, emergency in question and conditions).
My point is, she ran a dive trip operation in Thailand. I'm guessing she acted as a dive guide at times for tourist dive groups? If so, then she might've grown accustomed to a self-reliant diving mentality, and even supervising a group of divers of varied competency (customers) while doing so.
For someone with that background to be willing to dive at more distance from buddies than some might consider 'proper' wouldn't be all that surprising.
Brings to my mind forum discussions where different diver perspectives are compared; some strongly believe in self-reliance, to the extent of not assuming assistance will be available, and some believe strongly in the 'team' approach, an example being a team of GUE DIR-trained divers with standardized gear configurations familiar with each other & one another's gear. With such divergent viewpoints, divers who don't dive together regularly over time are often not on the same page with buddy practices.
All speculation on my part. Take it for what it is (or is not) worth.
Richard.