I Have A 90 Year Old That Has Been Having

I have a 90 year old that has been having frequent bouts of diarrhea, vomiting, stomach pain. She feels extremely ill. This has been going on for about a year. She sometimes goes about three weeks between episodes. I thought she might have IBS but she seems to be sick. I believe she is vomiting more of a bile substance. She has had her gallbladder out, eight inches of her colon removed and had hernia surgery but they were all many years ago.