Very judgemental to call a home you've not seen a hovel. Sorry, it's not a nice thing to say. A d psychoanalysing from afar based on just a few sentences, how professional is that. My late til used to do that to me, and he got it all wrong, but wouldn't have any of it so face up with the truth. I realised eventually that it seemed to be projection on his part, from things he said about his upbringing, nothing to do with tidiness mind, but since then I've taken such behaviour with a pinch of salt and reckoned it said more about the person doing it than the person spoken about. Tidiness can be pathological too I think. My brother drives mum and me mad moving things around for tidiness sake, supposedly, but ends up causing chaos as no k e can find where he's out things, unnecessary as really things were not untidy in the first place, he throws things away too without asking, and hides things, not sure if his motivation, but some of it is gaslighting I'm sure.
If you don't want to visit a messy friend don't, meet up elsewhere, or invite her to yours.
Please don't take it upon yourself to get rid of things. An old couple I used to visit were dreadfully upset when their children three away some of their mementos. What really upset them was when they tflhree away a map which they had marked places they visited and they enjoyed Fermi having a out past bolidays. Took up hardly any space at all, that was so thoughtless of them.
A friend's partner kept cider bottles as mementos, she tried to get him to just keep the labels, but no, needed the bottles too, all of them not just a sample one if each brew. I'd find that hard to cope with.
One thing that bugs me is partially used bottles or packets of things, so when children were at home I'd decent the final few inches into one bottle of the same, eg shampoo, body wash etc. Once that was done there was much more room in the bathroom. But I'd not do it at anyone else's. Don't anyone be passive aggressive either with a Marie Kondo book. Others might see faults in you that you don't see yourself, would you like a friend to give you a fat fighters cook book, .mouthwash or deodorant as a pressie. Obviously if you suspect friend is being abused it might be a kindness to give them the freedom program book,