Oh, I'm so very sorry to read this. It's is so very, very hard to come to terms with a diagnosis like this.
I was where you are this last time last year with my dear Mum who had stomach cancer. This was followed in August by my Dad's very sudden illness and death. Mum died in October. Both of them were in their mid-60s, and had been very healthy, active, clean-living people. It made no sense. It still doesn't.
I'm so sorry to hear that there is going to be no treatment for your mum. My mum had treatment (with the sole aim of prolonging her life- but I'm not sure there's much evidence from the medical community that there is any significant gain in life expectancy in such cases), and actually, having the chemo was at the expense of quality of life, I suspect. It was utterly awful and put mum in hospital, almost starving to death. Dad didn't have treatment though. He had multiple, fast-spreading tumours in his brain and there was no option for treatment at all.
I'm sorry, I wanted to post here to offer you support because my heart hurts for you, but instead I seem to have waffled on about my own family.
I have no good advice for you at this stage, other than just to be very gentle with yourself. Do you have a partner? Any siblings? How are your mum and dad feeling?
I wish I could say or do something to help but I know I can't and it's just the shittest thing. Sending un-MNy virtual hugs to you.