thank you for your query.
your symptoms point towards viral infection mostly the flu
is not a part of the flu but it is seen in some adults approx 6-10%.
since it is a viral affliction,antibiotics wont work and you to wait for the virus to pass out.just like in your case,your mother's symptoms will also subside in few days.
till then i would advise
-take lots of fluids to prevent dehydration
-don't take outside food
-avoid strenuous exercise.
if the diarrhoea is lasting for more than two days you can take anti-diarrhoeal drugs for symptomatic relief.
wishing you good health