The problem with doing that sort of mileage every day is that you miss it all. You don't get a chance to stop and admire the view, visit places en-route or have a lie in. I'm not knocking what she has done - fair play to her, good effort. But the speed she will have had to have walked will mean a lot of the scenery will have passed her by.
People tend to see what interests them on a walk. A keen ornithologist may see over 40 species of birds (so I am told) whereas I see colourful fluttery things, big black jobs and ducks.
How many people, like me, on the PW have stopped to see the Beacon Guards Grave 200m off the main route or deviated to include the summit of Fountains Fell, explored the Padon Monument, or finished off on the high level route?? Not doing these things, however, does not detracted from their enjoyment.
I am sure that she saw many things that I would miss, but also missed many things that I would have seen. Her pleasure, I would imagine, is speed walking. In my opinion, this is just another valid usage of a national trail.