Deteriorating Mental Condition

My grandma has become less responsive in the past couple of days; I'm afraid that her mind is deteriorating. Sometimes when I talk to her now, she doesn't even look at my eyes. But sometimes she seems ok. Today when I went to visit her, she was barely acknowledging my presence, but by the time I left she was quite alert. So it seems like whatever is effecting her condition, it's effecting her on and off. Sadly, I don't know anything about the human brain and I don't have easy access to a neurologist, so all I can do is guess what's happening.

I'm preparing myself for my grandma's deteriorating mental condition, but it's really difficult.