This irks me no end, because it's just a lack of forward planning on her part. If she wanted XP on her computer she should have looked to see which versions she was allowed to downgrade from before buying a computer, like the rest of us do. I've had this from relatives who've bought home basic to try out and decided it wasn't good enough despite my advising them not to!
To me her case sounds ludicrous.
"I bought this jar of marmalade only to discover it was orange flavoured, and I wanted it to taste like chocolate. Now I'm being told that if I want it to be chocolate flavoured I have to buy this stuff called chocolate spread in a completely new jar when I've already paid for this one that I don't want. Why can't they put it in the one I've got? It's an outrage!"