Hello
@evemc99 and welcome to this friendly and supportive forum.
I am sorry to read of your Mum's recent dementia diagnosis. I am pleased to learn that she has a carer to help walk her, and hopefully is able to do more to support your Mum,
Often people with dementia will insist things have been moved, or strangers gave been in the house etc. It sounds lime she is confabulating, telling a story that doesn't exist, but for her, it did. There is no reasoning at this point, as if you argue that nothing has been moved, then you won't win I'm afraid. Just run with it, something like ' well let's put things back where they should be' or the like. I know it's treating them like children, but that's exactly how the parent/child relationship reverts with trying to support people with dementia.
I hope this helps; I'm sure others will be along shortly with their suggestion too.
Please remember, you will always find true understanding and empathy here.