In a similar situation. Age Concern have a book I found very helpful sorting out in my own head what I could & could not do to help someone who does not necessarily agree with me about what needs doing. It also has a lot of practical info. The book is "Caring for Someone at a Distance by Julie Spencer-Cingoz. You can get it from Amazon or see more details about it on Amazon's website: http://www.amazon.co.uk/Caring-Someone-Distance-Carers-Handbook/dp/0862423678/ref=sr_1_1?ie=UTF8&s=books&qid=1245669594&sr=8-1
I also spoke to my Mum's GP about my concerns re her health & memory loss. The GP was able to persuade my mum to visit the local memory clinic for tests, & sort out better arrangemnts to help mum remember her medication etc..