Thank you for the query.
If someone survives 10 years after cancer treatment, we can say this person is completely healed from the cancer. However that kind of surgery (especially partial stomach removal) is a risk of new cancer. That is why, patients after such surgery needs to be under permanent control (gastroscopy and abdominal CTs should be done).
It is hard to tell if its just an acid reflux
or cancer. That is why, she should not be waiting longer and have gastroscopy and abdominal CT done. Please visit your doctor and consider this tests.
Hope this will help.