hallucinations after gastric bypass

A family member is experiencing hallucionations and is acting delusional. She will be ok one minute and the next she is talking about things that happened years ago referring to them as if they occurred yesterday. She is also seeing people who are not there not like ghosts, but family members who do exist but just are there presently when she thi nks they are. She has been in and out of doctors offices and been diagnosed bi polar. BUt I am bi polar and have never experienced what she is going through and she really believes in what she is saying and seeing. She had gastric bipass surgery 2 yrs ago, a stroke a year ago ande take xanax for anxiety along with heart meds, and depression meds. I am concerned the docs may not be diagnosing her correctly maybe because she isn't telling them all that she is experiencin g because she thinks it is real so she doesn't see the problem. can you give me some advice on what this could be or what steps to take next.