Well I'm going to go against all this "good advice" here and say that's what is being described is actually neglect, a pervasive and very damaging form of abuse. Yes that serious! It damages the little girls self esteem as she will be picked on and ostracised in school by her peers, have less support at home than she should, be unable bring friends home etc because she will feel shame for her surroundings. Does she not deserve to live in a clean home? What if she has no bed/bedding to sleep on? Is that ok too? Then what about meals? If mum neglects the home then does she neglect regular good food too? This can't go on! And the question is why is mum like this? Is it poor mental health, drink/drugs maybe or simply overwhelmed by being a single parent? She needs help to change this, not collusion to keep it quiet! As a social worker for 11 years I've witnessed the long term damage a neglected child suffers. Talk to the school and see if they have noticed smells, signs of lack of care (although will be lessened by the time spent with her gran) and if so then share your own worries and observations then ask them to make a referral to social services as they are legally bound to do. If they haven't noticed anything then Gran should gently offer assistance, suggest agencies like Banardos or local services equivalents to support mum to make changes for the better. If she won't engage then don't worry about your DIL relationship, worry about your gd welfare. PLEASE act on this ASAP.