Mother refuses to discuss advanced care directive - what to do?

Apologies for the long read but this is a bit complex.

Everyone describes my 92-year-old mother as a wonder. She shops online, does Tai Chi, downloads e-books and can discuss current politics. She lives in an independent villa in a retirement village. However she is also reclusive and prone to anxiety.

About 5 weeks ago she fell and broke her pelvis. In the medical ward, she became agitated when the medical staff asked if they could locate her advanced care directive (she has always refused to talk about this). Mum raised this with me the next day and started talking about how doctors and family use directives to collude to kill old people and gave an example of something she believed had occurred with a distant family member (no evidence). I was extremely distressed but thought this conversation might be due to shock etc. I am her POA for finance and care and welfare - there is no other family except for two grandchildren living overseas.

To put this in context, I left home at the age of 16, have never asked or taken money from my parents and I am financially stable. My mother lives 2 hours drive away (does not want to move closer) and I have spent lots of money and time driving and organising her finances.

I approached our family lawyers about the ethics of continuing as her POA and they felt it was important she wrote something down about her wishes and they also suggested a second POA might make her feel more secure. They said if I withdrew, there was a risk she would not appoint anyone.

Mum is now recovering in a rehabilitation hospital for older people and is preparing to go home. As she seemed quite relaxed, I raised this issue again and asked her if she felt I would behave like this family member who "had killed his mother." She nodded and said - slightly sarcastically - that I would behave according to my world view. I felt like bursting into tears but reminded myself I am her POA and told her that my world view should not have anything to do with it - my role was to enact her wishes if she was not able to do that herself. I told her I could no longer act as her POA for health without any direction. She said she would look at the care papers and I suggested she could just write something herself if she believed the template was coercive. She has not done so.

In the meantime the rehabilitation hospital has been assessing mum thoroughly over the past 4 weeks. They say there is some evidence of cognitive decline but that is age-related only (not dementia). They agree she suffers from anxiety. What has really shocked me is they have told me that what she says to me and how she acts with me is completely different to how she acts and talks to other people. They have said I need to protect myself (in those words) and have extremely good boundaries. They said she does not see people as people - especially me.

I guess I always knew this but refused to accept it in my heart. However, I do not feel I can abandon my mother now she is 92-years-old. It feels a little late to have come to this understanding and there is a duty of care. This situation is also complicated by the fact that one of our young adult sons died tragically recently, my husband has been diagnosed with Parkinson's and was operated on yesterday for melanoma - so my resilience is really low. Mum knew about yesterday's operation and that it was also the anniversary of our son's death but rang at 4.30pm with a list of demands that needed to happen by 5pm. I checked with the hospital - those were not real.

Any advice about the POA and Advanced Care Directive would be appreciated.