Need to know in detail the current disease status of patient and treatment already received to comment . You can consult and and will be happy to talk to your mother and explain to her what needs to be done

Chemotherapy drugs have the side effects of causing peripheral neuropathy/ myalgias. They will cause this symptoms of weakness, numbness, pain, paresthesias. Generally these are present during chemotherapy and later they gradually subside. Sometimes instead of reducing they become severe with every chemotherapy cycle. In such scenario, treating doctor will examine and decide if the drug dose needs to be reduced or to stop the drug completely and change to another drug if symptoms are very severe. Some relief can be sought by neuropathic pain relieving agents like pregabalin if paresthesias are persistent.