Last night I typed a lovely long message last night, pressed 'go' but the link dropped out

My suggestion was that some medications can cause alteration of taste as can lack of minerals, i.e. zinc.
Lemon sole can be tasteless anyway. Also, if there is butter on her spuds i.e. mash, then the oil can cause upset bowels. Onions? these upset me within 12 hours

- usually downwards.
Have a look at a Jewish cookbook, apparently chicken soup cures most ills!

…… bland food is good for upset tums and scrambled egg was suggested years ago for recovering patients. Or a poached egg? I can't tolerate eggs.
Diced chicken: grilled: on a bed of plain boiled rice? Add salt and pepper for taste. Same with fish, something more tasty like mackerel fillets if oil isn't make her bowel runny. Again, a bed of plain rice.
Rice pudding from a tin? Semonlina? lines the gut. Also, LIVE yoghurt and Actimel to assist 'bacteria'.