I found with people with dementia respond much better when you just agree with most of what they say, responding negatively seems to exacerbate their behaviour. I'm sure you probably know that anyway, I'm sure your sister will be so grateful and knowing that will get you through..
Cookery books and other books - are you keeping them ?
Fascinating causes of death 1632
Energy Firms Want Government To Step In Over Winter Bills.....


Things said in a positive tone seem to encourage a positive response - hard work but worth it for the time you are there. 
