Women always want new stuff. They are never satisfied with what they have. There is nothing you can do about it.
I just bought my wife a car last year, now she wants a new car again. I would love to give here anything she wants, but I don't make enough money to afford that kind of life style.
If your bed room set is important to you because your grandmother got it for you, then you just need to explain that over and over in different ways until she get it. If she doesn't get it, well then.....