Advice on ceasing treatment

Hi everyone

I hope someone can help me, this journey is horrible. 

My mum was successfully treated for breast cancer 9 years ago. Last year it returned with aggression.

It attacked her intestine, peritoneal region ending in emergency surgery. She had 12 cycles of abraxane chemotherapy and was in remission. So placed on Femaras as maintenance.

Four months later, markers began rising rapidly. PET /CT showed new activity all through the peritoneal region.

We opted for the Ibrance + Examestene. At this time Ibrance was $5k per month but as it had such good resulted. We paid for it.

Ibrance had no impact on tumour markers, they continued rising and mum got sicker and very nauseated. Another PET/CT after 3 months treatment with Ibrance showed extensive liver mets. So many they couldn't count. And disease in the peritoneal region widespread.

She was immediately taken off ibrance and placed on Eribulin chemotherapy. Markers started dropping and liver function was improving. We were told things were stabling and we shared a sigh of relief. They said she could stay on eribulin as long as it work.

Then suddenly she wasn't tolerating it as well. Fatigued, dizzy, just laying on an armchair everyday with no energy and she lost 4kg rapidly.  They repeated blood work but everything was fine. Then she started to feel a pulling ache in her right side so they did a CT scan and found her liver was massively enlarged, deformed and so bad that they couldn't even make out what was inside of it.. 

Upon seeing that image and seeing how unwell my mum was the oncologist advised he saw no reason to continue treatment. That her quality of life was poor and for the liver to be in such a bad state it's likely full of cancer and she will die soon. He couldn't say when she will die. Just soon.

So he sent us home and called palliative care.to set things up for mum to die at home. 

This was 20 days ago. In the meantime, mum was happy to be off chemo.. Her energy returned, her apetitite returned. She began doing things around the house again, we went out, she gained 3kg.. And looks so much better.

We decided for a second opinion and saw a new oncologist . He re did blood work and her tumour markers have risen, and her liver function is now very much deranged.. And has deteriorated in virtually a month . Chemo toxicity cannot be fully blamed when she hasn't been on chemo for a month. 

He advised she could try a tablet chemotherapy called xeloda which he said would be well tolerated and may buy time. Without treatment he said she would die in a matter of weeks as the liver function is heading toward failure. 

I can't understand how all this is happening when she looks so good and has had the best 20 days in a very long time. But she is dying. 

Mum doesn't know whether to enjoy what is left drug free, or whether to take the drugs which may buy time but how will it impact her quality of life?

This is a nightmare  I don't want to let her go but I don't want her to suffer. Her metastatic journey has only been 15 months . Not even the average and even with trying brand new drugs.. I'm just shattered. 

My dad wants to try CBD oil which we have legal through a doctor but it's apparently metabolised via the liver and can impact liver function. This oncologist doesn't want her to have it.

I'm heart broken.