My dad's symptoms were very different. Stomach cancer is often misdiagnosed as it generally presents like an ulcer. He said it felt like he had swallowed hot coals. Then he would occasionally throw up something that looked like Coke. It was old blood. Sorry this is so graphic but cancer is a graphic and ugly thing.
He was treated, at first, for an ulcer. Then after not getting any relief, he went for an upper GI. That's when the biopsy was taken. 2 weeks later, he was diagnosed with stage 4 stomach cancer.
Stomach cancer is pretty hard to detect as it shows no symptoms in the early stages. As you will learn on this board, most people who are diagnosed are already in an advanced stage of disease.
Good luck. Hope things go well with your mom. Keep us posted!