i think that children who can't be bothered are using the "can't be bothered" mentality as a form of social identity.
social identity seems to be pretty big - a teen needs to know itsniche - its place what strata it fits into.
my 17 year old has gone from ( self professed) chav ( townie) to rock god iron maiden rule over the last year.
my 13 yo is an Emo fringe over eyes - bit gothic but likes pink too much
they have created their own image.
now, i truly believe this is whaty our daughters doing.
you need to help her - she has low self esteem and has lost her place.
i dont care if she is butt ugly and as fat as the michelin man ( which she prob isn't) she will love money spent on clothes, make up cosmetics, shoes, pampering, smelly gift sets ( loads now its xmas time)
help her create her image - tell her your willing to spend the money but shes got to hold up her end of the bargain and have a shower at least twice a week.
if you haven't got the money - save it up. she needs it.
sit down and discuss her preferred style - what miche is she wanting to fit into. does she want to be a townie, rock chic, emo.....
this also goes with keeping own space tidy and manageable - so make a certain day - tidy your room day. this also helps with studying and teenage morbid thoughts