There are many different remdies for pain.  if she is on morphine, the herb panax ginseng can protect against some of its adverse effects and help her reduce the dosage of morphine needed.  If the pain is caused by a tumor impinging on nerves then GLA from borage or evening primrose oil would help as well as B12 either IM or sublingual, and magnesium (200-400mg).  If inflammation is the cause then curcumin, boswellia, scutellaria (skullcap) or salix alba would be good choices.  To reduce her sensitivity to pain corydalis would be worth trying.  For the cancer there is a product that has promise called AveMar. You can find it on the internet. Ihave seens some studies that show that it slows down some cancers. High dose vitamin would be worthwhile on the days that chemotherapy is Not used and curcumin has been shown in animal studies to cause tumor cells to die.  I recommend her seeing a licensed ND if there is one in your area.