hello.. low back ache stomach upset and white tongue swollen.. is she taking any other medication other than the above said?does she have burning sensation in urine?fevers? i would advise you to get a CBP urine analysis kidney and liver functions done.. causes are multiple for the above said problems.. so it is better you take her to a surgeon and get a thorough clinical examination done followed by above said blood workup and an USG scan,any other blood test felt necessary by your doctor.. she may have infection in her kidneys or abdomen..if that is the case she needs to take a course of antibiotics along with other supporting meds..which will solves the problem coated tongue can be due to drugs she is taking now or due to fungal infection or simply due to dehydration.. try oral candid gel for applying on tongue..this helps if it is due to fungal infection.. hope this helps you.. if you have anymore questions feel free to ask me..