My mother in law has bowel cancer, Finding this difficult to deal with>>?

My partners mum was diagnosed with bowel cancer 4 weeks ago. The hospital said things would move fast, but now 4 weeks on they are only beginning treatment. It has spread to her liver and lungs. She will be taking chemotherapy tablets at home. God it's so hard seeing her deteriote before our eyes. She used to be a size 16-18 but now she's about an 8. She can hardly walk n talk much, we have stayed over some nights to help her but we have 2 very young children so it's quite hard. My partners brother and sisters never offer to stay the night. They all act like everything will be ok but I've a feeling she won't last. Please offer me some guidance if you have gone through this before. My mother in law is 61 years old.