What should I do?

No, Mom does not have Dementia based on this conversation. You think 46 is cold Mom doesn't. You starting arguing, Mom asked to drop it. You should have dropped it.

Arripley,
In this case, it appears that you are watching T.V. and are instead making conversation that your Mother asked you to drop. Instead, you are disagreeing with her answer, you are judging her, telling her that she does not make sense.

Some people do not want to talk while watching T.V.

You could have avoided a disagreement if at this point you just stopped talking: "I asked Mom 46 degrees is cold isn't it because it was going to be 46 degrees tonight. She said no that's not cold."

Mom is entitled to her opinion?

Seems like a silly thing to start an argument over. 46 degrees isn’t very cold.

What was the big deal?

I am a 64 year old woman originally from Wisconsin, now living in North Carolina, and I have to agree with your mom that 46 degrees is not cold. Perhaps a little cool, but not cold.
I remember when I lived in WI, and it got up to 50 degrees in the early spring how many people I saw running around in shorts because people were so tired of the long and yes very cold winter, and they finally had hope that warmer temps were coming, so they(prematurely perhaps)put on their shorts.
So this actually boils down to ones perspective and has absolutely nothing to do with your mom having any kind of dementia.
So next time you don't agree with your mom, just agree to disagree, and quit making a mountain out of a mole hill. It's really not worth it.

Welcome to AC Forum. I am thrilled to learn that this minor disagreement about how one experiences heat and cold is the worst of it for you! I don't think that I would spend a whole lot of time arguing this particular point. You seem a bit focused on this minor tift, so I am guessing that disagreements are rare and few and far between for the two of you, and that whatever was on TV wasn't particularly engaging that night.

Next time I would just switch channels and find something more interesting to watch.

It could be dementia, it could not be, it could be she is just frustrated, older and lots of aches and pains and didn't feel like arguing with you about,what's cold and what's not cold. As for hearing issues, it doesn't sound that way to me. She would of said, What, and probably said you where not talking loud enough

HI! It sounds to me that she just didn't want to belabor over talking about the weather! Maybe it wasn't that big of a deal to her and not much more to say on the topic.

I don't understand why you asked the question in the first place, if you knew the answer. Then you argued about it.

I agree that you were making a big deal about it and should have dropped it!

This interaction doesn't give any indication of dementia.

Is this the only thing that you are basing the possibility of dementia on? The weather?

Maybe your mom was thinking that 46 degrees isn’t freezing. Or, how bitterly cold it is in other places.

Don’t sweat the small stuff. It’s not worth getting upset over.

If other things are happening, and they happen regularly, then you can address the issue.

Arriple,
People who have lived in a colder part of the US might think 46 degrees is warm. What's the big deal?? During the winter months in Massachusetts, I usually don't like my thermostat above 62degrees. When I am outside during the winter I don't think 46 degrees is cold. I feel your communication style with your mother is more than harsh.
Just so you know people in this forum are not qualified to diagnose dementia or hearing loss.
If you are worried, ask her to have a hearing test. She would need to see a neurologist for cognitive testing for dementia. Sometimes they order brain sans to look for volume loss or changes in specific areas. I think you may be over thinking this. Not every elder gets dementia.
I wish you and your mother the best.