I, too, am sorry for what you are going through.
She has to keep her head at least slightly elevated. So, not in a hospital bed, but sleeps on 2 or 3 pillows. We have a friend that had a partial gatrectomy and he had to sleep with his head more elevated than my wife. He has since had a recurrence and they went in a took the rest of his stomach and his esophagus and is now in remission.
My wife lost a bit of weight too. She was lean to start with, but lost about 30% of her body weight.
Some things she's learned is to make sure she has protein with every meal. It slows down digestion and balances out her system. Also eat rich foods such as spaghetti, lasagna, foods with gravies, etc. Now, with a reduced stomach, you can eat anything your body can tolerate and not worry about gaining weight, so have fun. I know that's not always easy, but at least its a bright side.
Hang in there. You can win!
Greg