I'll try to keep this brief but it may end up long (sorry!).
My Nana is 86. 10 years ago she was diagnosed with breast cancer in both breasts. Mastectomy done on the worst side. Some radiotherapy on the other side. For a few years, things were as ok as they can be (we were lucky I know!).
Anyhow, a few years later, we found out Nana has bone metastases. No treatment as she was older/more frail. She hasn't been well for a few years but we have been plodding on. She has continued to live in her flat with support from family. She had a bad episode last year and we were told she had developed diabetes (diet controlled, no medication).
The last two weeks, it's all gone a bit wrong. Over this period she has been sleeping loads and barely eating. I had to call an ambulance Monday as she hadn't eaten for nearly two days, barely drinking and was unresponsive.
Hospital brought the blood sugars up but also found she has had a heart attack and a scan/bloods show abnormality of liver.
Basically, she is extremely frail so nothing to be done for the heart (not for resuscitation either). From speaking to the doctors and given her symptoms it looks like the metastases have spread to the liver. They won't investigate further because there would be no treatment done (fair enough).
So, essentially, they have said she can go home (which she wants) and i am awaiting a call from the social care team about support in place for when she comes home. I plan to contact Macmillan on Mon.
I'm utterly exhausted and overwhelmed 
I want her to be where she is happiest which is at home (if possible). However, I am concerned that she won't eat/drink enough to maintain blood sugar and may not drink enough of the special sugary drinks they are sending home to maintain blood sugars.
Stupid as it sounds, I don't know what to do if/when she deteriorates further. I feel like calling an ambulance isn't the right thing because they can't do anything. So is it just GP/Macmillan?
I suppose I have to face the fact that we are in the end of life stage but it's so, so hard. I work full time and have a little boy so although I do what I can, I am limited as are other family members which is why I am asking social care/Macmillan for support now as we can't continue as we are.
Sorry for rambling- I am close to my Nan and this week has almost broken me emotionally and physically. I am utterly exhausted.