Because Czech. The word order is wildly flexible. That does not mean that it can be any. So K sýr neji x K nejí sýr is the same thing. It seems though that the first one gives more emphasis on the fact that she does not eat cheese. Like i already told you 3 times that she does not eat cheese and you still insist on buying her aged parmesan for Christmas. To which I go "K sýr NEJÍ!!!