Grandma getting confused and saying things that aren't true - some about me. What do I do?

My uncle (Grandma's son) came over to my house to visit Grandma yesterday. I was in Grandma's bedroom across the hall doing chores, but could hear parts of their conversation. Approximately 45 min. after he got there, Grandma told him she was hungry and that I did not feed her supper! This was about 70 min. after she had just eaten her normal supper. I didn't want to say anything because I didn't want anyone to think I was eavesdropping. I can't help it that the walls are thin though.

Additionally, I heard her say a few other things that were not right about people or events. She said her sister had recently visited, but she hasn't been there in over a month. The other things she said about people or events were insignificant, but they were still untrue.

So about 20 min. after she said she hadn't eaten, she asked her son to get a jello cup out of the fridge on his way back from the bathroom. I took this opportunity to go check with Grandma and caught her son in the kitchen. He said she hadn't had supper and I told him she had finished eating about 30 min. or so before he had arrived. I said she gets confused and forgets things (which he should already know) and he said maybe she was just hungry then. We laughed about it so I guess it's ok.

I've known Grandma's memory hasn't been good for 15 years, even back when she was still getting around perfectly fine on her own. Considering that her memory has been noticeably bad for the last 5 years, I find it highly disturbing that anyone might even consider believing her when she says I didn't feed her a meal. Even before she lived with me, I knew her well enough to not believe everything she says. I take everything with a grain of salt.

I find this matter to be really upsetting but I'm not sure exactly why. I don't know if it's because this is basically the first bad thing she's said about me (that I know of) or if it's because someone might actually believe it.

I'm considering contacting the two or three people who visit her on a regular basis to let them know about this incident. I would like them to know that if she says something like this again and they are concerned about it, to talk to me because it's most likely not true. Grandma has access to her own food that she can get at anytime and often does. She really goes through the snack cups in the fridge (jello, fruit, pudding, yogurt). She gets one out in the early morning before I wake up and she eats them in the middle of the day and before lunch. If I have chores that keep me super busy, I'll leave her a sandwich in the fridge, or some PB crackers or a cereal bar on the table. The point is, she won't starve because she knows where the food is and can get it on her own.

I'm wondering what others think about this? What should I do?

As a side note, it kills me when Grandma tells old stories to people (particularly the younger grandchildren) and everything she says is different then when she told the stories repeatedly years ago. She gets years, events, and people wrong. It just seems ashame that those who don't know better (the other grandchildren) are hearing inaccurate recollections of her life.