Poor absorption as in irritable bowel syndromes and malabsorption syndromes too is possible. Malabsorption syndromes are seen
in intestinal tuberculosis, HIV, tropical sprue, parasites
in stool and Whipple’s Disease. Diabetes too can be the cause.
Since gut cancers and leukemia, lymphoma are ruled out, your mother should consult her gynecologist and urologist to look into causes and cancers related to uterus, cervix, vagina, ovary, bladder etc.