Your update confuses me - I imagined the house to be in a horrific state, but given that you've also said "could easily be done in a day", it can't be all that bad at all.
Anyway, best thing I think you can do is try to find her a boyfriend who doesn't car about the mess, because that's what she's after. In fact, you could almost say that it's as much of a perquisite as any other feature would be - we all have our ideal types and hopes as to what they will be like.
I know of two couples who live in what can only be described as what looks like the aftermath of an earthquake, and yet they are all as bad as each other. I swear it's the "couldn't give a toss about it" quality they possess which allows them to be so devoted to each other.
You also ask How do people's mind sets get changed in situations like this? I guess the same as they might with anything else - living life can, in itself, be the game-changer, seeing how we are all liable to have different needs which change as we age. Likewise our priorities change, our attitudes change, our goals change, and so on.
I am lucky, because I can be ruthless and very pragmatic when it comes to "things", and I will die on the hill that my home is more than big enough for two adults, therefore if I catch myself thinking I need more storage, I tell myself that no, I need less things. Then I begin a de-clutter accordingly.
We all have stuff we don't want to or can't part with - for reasons I won't bore you with, I have two washing machines as one is used for work. This is essential for what I do, and my home has to accommodate it as it's non-negotiable, but that's not what "normal" homes would have. I am also a sod for keeping stacks and stacks of bed linen, as pillow cases & duvet covers can always be used as underslips for the main covers.
But clothes, shoes, anything like that, I try very hard to keep on top of, and frequently tell myself I don't need any more clothes or shoes, because what I am actually needing is opportunities to wear them. I don't get to wear 3/4 of what I own, and I only have one double wardrobe full of clothes.
Hoewever, when it comes to chocolate, my discipline is much less present. We're all different.