Worries about mum’s treatment for ovarian cancer

I live in the UK and my mum is in Poland. My mum has been going through ovarian cancer treatment for last 2.5 years and recently her health has really deteriorated and I’m worried they will not be able to give her chemo anymore. She is barely eating, and yesterday could not go for her chemo appointment due to being really ill. My aunt took her eventually to get some IV fluids which helped. Mum also has depression which makes her not want to do anything and is really draining on my aunt and my dad who look after her. 
I have always kept positive and now I am really struggling. I went for a visit a few weeks ago and was shocked how bad she was. I managed to convince her to get some more help for her depression, thought things would be getting better but they seem to be getting worse. 
Since being back to the UK, my mental health has taken a nosedive, I am struggling with anxiety, low moods and I think some anticipatory grief. Sleep has been affected, small things feel hard. Work is very hard. I started counselling and took some time off sick to recharge my batteries so hoping this will help. 
I’m struggling to cope with this situation, I can’t be in Poland at the moment and cannot give up my life to go look after her full time. I hope taking time off work helps my mental health so I can better cope. This is so hard and it’s difficult to watch things from afar.