My Sister Got A Flu Shot A Week Ago Friday

My sister got a flu shot a week ago Friday while she had a cold. On Saturday night she woke up nauseated, throwing up and had loose stools. A week later she still doesn't have an appetite, has a metal taste in her month and throws up about every other night. She still has a cold too. what could this be. She is 69 years old. Had some of colon removed 16 years ago due to colon cancer. Has been cancer free since.