She actually died and was brought back. She says she is in wrong house and forgot all her bills, want go back to doctor or take meds. she remembers years ago but not yesterday. she thinks we switch houses on her. This goes on everyday about the house. One day its right, the next she claims we move her, we just agree should we tell her it is her one and only house?
Rinse. Repeat.
She is suffering from short-term/recent memory loss, a condition that often affects those whose heart has been stopped and whose brain has been deprived of oxygen for any length of time.
I see the advice already offered to you, but please understand that your sister may now be unable to process information however kindly it is given to her. That uis why you need to be the understandingone and be as gentle and kind to her as possible.
It is a folly to believe that firmness will make her understand what she has gone through and settle her mind. If she were capable of understanding she would have understood by now.
Whether time will heal her or bring back her lost memory, time alone can tell. But, whatever happens, she is as she is, and if she does not change, improve, or recover, then your role is to make her as happy and as comfortable as possible.
Talk about the old times; the times she does remember, and if there are friends from those years, have them visit her to talk about them.
You can be as affirming as you need to be if it will settle her mind. If, however, as seems likely from what you say, then you might just have to go along with her if it helps her find her way through the confusion that her condition has imposed.
What she remembers, does not remember, or imagines has happened to her is, to her, superlatively real, and no amount of mental gymnastics, trickery, or hocus-pocus psychobabble course corrections suggested by the well-meaning but uninformed will change that unless and until [IF] she recovers her memory sufficiently to know this for herself.
Until then, take the philosophical view that she is safe and well and keep her that way. I have found it is best not to argue with what may be delusions because all that results from that approach is tension, hurt feelings, unhappiness, depression and misery for all concerned.
Be grateful that your sister has survived, despite the changes you see in her.
I wish you the very best of luck with your dear sister. The future, no one knows. However, you can make it the best you can by being loving, kind, and gentle, as sisters ought to be to their loved ones that are hurt.
:)