Surgery questions

Ditto on the response from baw644. If your aunt's esophageal valve to the stomach is removed there is nothing to keep the food in the stomach except gravity. If she lays down after eating she must be sure to keep her upper body elevated to prevent food from coming back up. My doctor put me on Prilosec, an acid reducer which has helped greatly with my digestion. Your aunt may need to try several different drugs to find the acid (proton pump) reducing drug that is appropriate for her. The first ones they tried made me nauseated.
Getting used to the frequent small meals can be a challenge as most folks are so ingrained with the three meal a day routine.
I did find that my tastes changed also. Certain things I don't care for anymore and other things I did not used to like I enjoy eating.
One of the things you need to watch out for is extreme and/or rapid weight loss. I was on a feeding tube for a period of time. If the docs place a feeding tube I would suggest your aunt leave it in for as long as possible to be able to supplement oral food intake. I was tempted several times to remove my jejunostomy(small intestine feeding tube)due to a little discomfort and the 'hassle' associated with being hooked up to a food bag and pump to deliver liquid nutrition. I wouldn't remove it unless medically necessary or until she is certain that she can orally intake an adequate amount of food. Honestly, it can be difficult at times for the post surgical patient to eat. Family and friends support is so important during this time of recovery. She is lucky to have your support and she will definitely benefit from your gentle but firm insistence that she strive to eat.
I hope this helps. If you have other questions I will do my best to answer frankly. It won't always be easy but the surgery helped to save my life. Unless there is a better way to rid yourself of the tumor(s) in hindsight I wouldn't have done any different.
Good luck to you both.