Old age or Alzheimers?

Here's a little background since she has moved in with us.  June of 2004 we moved her here, in February of 2005 she was diagnosed with a cancerous tumor in her bladder. She went thru chemo and radiation with flying colors and is now cancer free.  She also has an Aortic Abdominal Anuerysm (sp?) which they will do nothing about because it's not that serious yet.  She is fairly healthy now with a small problem with high blood pressure and high cholesterol.  For being mostly blind she is very active and doesn't like to sit around. I just hope that I'm that active at her age!

Well like I said, I have been noticing things more and more that seems odd.  I will be in another room and I will hear her talk to herself and she denies doing it or she will talk at the tv.  She also has these emotional "meltdowns" from time to time though it seems to be getting more frequent.  She's got the idea in her head that my 10 year old daughter doesn't like her and will even tell her this which makes my daughter cry because she doesn't know what she is doing wrong.  She has never been physical with anyone though. She gets forgetful of sometimes everyday words and she always misplacing things in her room.  I've come learn her hiding spots very well by now.

So I am not sure if these things are an indication of anything more important.  I know that in the 1 1/2 years she had alot to deal with....losing her husband of 50+ years, moving out of state and in with us and getting cancer.  I am trying to supportive as possible but it's kind of breaking my heart because I've never had to deal with something like this and I don't like what she is doing(probably unintentional) toward my daughter.

So any ideas or suggestion?