Stomach swelling why? If it is so. ?

My mother age is 55, she is having a stomach problem.. Whenever she eats something heavy she is having a severe stomach pain, when we visit doctor he diagnose a stomach swelling and prescribe not to eat junk food and spicy food.. It is very difficult to stay away from this food every time.. However we take care of it that she eats at home but everytime it's not possible... Want to inquire  is there any other conditions too for this problem and if it is so.. What are the  blood test names we should do.. Because why she doesn't digest the food which others can easily eat and digest of her age.. Are there any other possibilities other than stomach swelling.. What are the blood test recommended if it is so...???