Why did she told me this?

A few months ago my mom ordered a new couch, and since she has never assembled the sofa, so earlier I sat on it, and she came and scolded me about not sitting on it, and that I have got dirty, and then put a big blanket over it so I couldn’t sit on it, and then she said that can’t sit on it since it’s her couch and she the one that payed it, why?

Why did she told me this?
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