My mother-in-law seems to be experiencing rapid short-term memory loss [View all]

In the last few months she's declined significantly, can't hold a thought or memory for more than 20 minutes. She's 69 (I think), recently retired. It's been obvious for a while, but not to this extent. My wife went up to spend a day or two with her and was appalled at how far she's degraded. I don't know if anyone has any ideas. Focusing on the obvious - alzheimers onset, tumor, whatever. She supposedly has a Dr. appt tomorrow.