Also when they are out of their environment of the home they can get like that. The only thing I would ask about her blood panels making sure everything is coming back normal such as potassium, sodium, and such. My mom at 93 had a bad case if diarrhea her sodium level got so low it was as if she had Alzheimer's for about two weeks. She normally is pretty clear, even has a Facebook acct.
How long has it been since surgery? You could always ask for a Neuro exam in about a week if she hasn't cleared up some.
I know I was worried my mom had a stroke or something so I know how you feel.