There are control pain drug,(pain relief drugs) something like cocaine(You Must be Kidding! Cocaine is ILLEGAL!!!), often in metastasis patients(Don't understand your English, you could say cancer patients who have metastasis), if she got(takes) fully(full) dosage, she will feel better than now(how could you be sure?).
you should ask (an) oncologist, they should be known those(they are experts/they should know what to advice).
I appreciate if you could regard people's benefits and rights as the highest priority with being responsible and mindful of science!!!