Hello dear
Warm  welcome to Healthcaremagic.com
I have evaluated your query for your mother in details  .
*  This is due to food 
poisoning from seafood .
*  Primary guidelines for better recovery
Allow her to consume plenty of liquids  in form of boiled water , lemon juice coconut water , home made juices , organic  tea , coffee , butter  milk  etc .
Prefer soft , light  , bland , vegan  diet  with fresh  curd  preferably .
Avoid  all types of  oily , spicy , non veg , hot beverages , junk foods , dairy fat , milk  , aerated drinks  till recovery .
Intake of PPI  ( as 
omeprazole ) , anti emetic as ondancetron help faster recovery , which requires prescription with your doctor .
Wishing her fine recovery .
Feel free to ask any further  queries .
Regards  .