Just because she's laughs and appears to think it's funny, doesn't mean there isn't something underlying it. The"funny" might be a coping mechanism, or something is going on with the wiring in her brain.
Pp who said this was bollocks, well despite your clear and scientific response, I would still argue that no one is "just" anything.
You rarely see any other animal live in its own mess, and generally it is human nature to keep some sort of order..at least in the food and sleeping areas.
Anyone who is living in squalor has a glitch somewhere.
As for those who proudly agree they're lazy - they've probably assumed that is what it is.
Lots of us tell ourselves we're lazy, stupid etc. Partly because we don't understand why we do things, partly because charming relatives tell us so. 
The 4 or 5 friends I know who really struggle with varying degrees of mess/squalor, have all told me they are just lazy at some point or another.
They have also, at other times, told me about their adhd, anxiety, abuse, etc etc. Incapable of creating boundaries for kids because they had such a miserable childhood they can't bear to tell them off. Staring at something that needs doing, but literally fell unable to start the project. Anxious at the very thought of throwing things away.
None of these are normal situations. None of them have ever made a link in their own minds.
Just got to their 50s still berating themselves for being stupid, thick, lazy, bad...
Even when you have had the links explained to you, it doesn't mean you can stop/ keep to a plan.
I'm probably wasting my breath. So much easier to judge people than try to understand.