Chemo for terminal cancer?

My mum has just been diagnosed with stage 4 terminal breast cancer. She has been offered chemotherapy to help prolong her life rather than cure. I am worried that doing so will make her quality of life a horrible time. They have said she will have 6 months without chemo and 1-2 years with... 

 

I really don't know what the best road to go down is... I'm 23 and my mum is going to be 60 in May. She is the only family I have.