Well if its a rare side effect than it probably isnt happening now. But to be on the safe side I would get her off the quinine and see if her memory improves. I knew an elderly lady once and she had leg cramps at night, the doctor gave her quinine but I never saw an improvement and I knew her for some months, never saw any memory loss though. The problem with the elderly is they sometimes cant burn off meds because they have mild liver or kidney problems that arent picked up on. Or they have a lot of drug interactions that its difficult to figure out whats happening..