How do we explain to my mom, who has Alzheimer's, that she cannot bring all of her household items when moving in with my brother?

Question

My mother has mild Alzheimers and has agreed to move in with my brother. She has her own room and her own bathroom. Other than her personal items that she can house in her own room and bathroom, she is insisting on bring several other items with her home such as dishes, furniture, curtains, etc. to go in other areas of his house. How do you suggest we apporach her that these additional items are not necessary to bring because his house is already furnished and equipped. She has made several comments like, I'm not throwing away my things, or the curtains in the kitchen need to be changed or what do you expect for me to do with my things that I have worked hard for. And when she make changes or bring items in, she never consults with my brother. There is really no room for her household things. There's only space her personal items for her room. I'm afraid she will get upset and decide she wants to go back home, so how do you suggest we handle it? I want her to understand that we want her in his house so we all can care for her but too, she can't bring along unnecessary items? Not only that there's no extra space but most of her household items are old and outdated. What should we do?

— Michelle in Winston-Salem, NC