Oh my goodness, I just typed out the longest message, and it completely disappeared!!!

Here is the short version....any opinions would be so very appreciated!
Over the past year my 79 y.o. grandmother has been exhibiting what I think is alarming cognitive decline. The rest of the family just kind of blows it all off as "normal aging", but I'm not so sure.
She is becoming increasingly forgetful. One day, she will have forgotten that the family Thanksgiving dinner will be held at a certain home this year, but the next, she will remember it fully, right down to what she decided a month ago that she would bring! She will ask one of her grandchildren (an only child) about her sister in Alabama, when the sister is really that of the grandchild's mother! When corrected, she will just shake her head and acknowledge that she "just got confused." She tells the same stories over and over again within a short period of time. We are a tight-knit family and all live close-by, so why is she telling us things that we are obviously very aware of? For example, she tells us all the time about my grandaddy's dog, who he takes to the farm with him everyday. (Yes, grandaddy's dog has been a special member of the family for more than 10 years!) And just last night she told me about her 9 y.o. tabby cat who does tricks...except she described him as a black tomcat with a "tuxedo" spot that died several years ago!
I talked to her on the phone for about 10 minutes last week, and within that time, she asked me
4 times where I was.
Keep in mind that my grandmother has for years been somewhat paranoid, anxious and contrary, but otherwise quite sane. I think that at the very least, she should be taken to a doctor for a definative diagnosis, but those decisions are left to my grandfather, mother and uncle, and they just seem to think it's all normal behavior and aren't that concerned. I would really appreciate the advice and/or opinions of those of you who have experienced this phenomena first hand. I don't know how to convince my family that it's time for some intervention!
Thanks so much!