I'm not arguing about her pay, that's up to the market. However, the condescending tone of your post shows that you have zero inkling of what's involved in the PhD process (no worries, most people don't even when they think they do). I've lived through my wifes years in PhD school (accounting). It was as intense a 5 years as I could imagine anyone enduring.
So I'm absolutely condescending of people who think because they went through a process of any kind they are automatically entitled to respect and high pay. I respect people who prove their worth to society.
My answer:
A difficult accomplishment should be its own reward irrespective of the outside world.
A useful difficult accomplishment will be rewarded by the outside world.
In her case she overlaps very heavily with behavioral economics (think freakonomics, predictably irrational, etc...). It can be pretty amusing watching these academics fight over what is in the realm of behavioral accounting and what is within economics. No one really knows;)
There is a capital markets side of accounting research which is much more focused on the analysis of accounting in the wild.
It is hard to sort of put your finger on what accounting research is. It does exist tho:)
If they have to argue about this, then they've probably drawn the dividing lines between their categories wrong, and they're trying to shoehorn new ideas into an ill-fitting taxonomy rather than making the taxonomy accurate.
(Related: where the hell does computer science fit? Is it a science, or a branch of applied math, or a craft, or an engineering discipline? Or perhaps an exotic species of potato? Sometimes I think we need the ghost of Alfred Korzybski to rise from the grave and harangue people.)
At that meeting I watched a woman with a doctorate in English scream at the future (and former) Mayor of California because he was telling her they'd have to cut her six figure salary. Even though she admitted her students test scores were abysmal and everyone in the room knows she couldn't go anywhere else and get paid the same rate she still felt she was entitled to the money on her degree alone.
Bottom line (IMHO): If society is to move forward people who deify the degree need to be relieved of that delusion even if it's painful to them.