I don't want this to sound like an attack but what's the issue? Heaven forbid someone feeds their pets the food they're supposed to eat instead of some hyper-processed and unregulated sawdust pellets.
Well if you assume that beef is bad and cheap beef is especially terrible for both the environment and the cattle themselves then it isn't a huge stretch to see why someone pouring 20X the amount a human would eat into 2 dogs every week could be viewed as immoral.
It's like more people driving hybrid/electric cars cause gas prices to go down, in response to this other people can now buy bigger gas guzzling cars. Economics rewards immoral behavior.
Governments spend a lot of money on agricultural subventions, especially on meat and milk production. So from the perspective how the taxpayer money is spent, these specific pets probably got more financial support than several poor families combined.
Of course, this is mostly a problem of the system being designed so that it is trivial to abuse it. But currently, the system is what it is, and the lady's behavior is what it is.
I am not an expert, but the dog food cookbook I have cooked from didn’t prescribe 100% meat, it had you combine meat, grains, vegetables, and oils (and eggs? I can’t remember).
And there are more sustainable meats than beef which are just as healthy for dogs.
Also using parts of the animal other than the prime cuts is good for an overall more sustainable plan. (And probably good for the health of the animal too)