OT, but flying to PRG a couple of weeks ago, the OH and I were sitting in 1DF.

A gentleman boarded and insisted he was sitting in 1F. A brief discussion followed, until the fact that I kept repeating that this was row 1, pointing to the number above the seat and asking to see his boarding pass obviously made him realise that he should be elsewhere and wandered off without saying anything more. I watched him go to row 7 (IIRC) which was the front row of ET, where he sat down, as I had expected.

Having used OLCI, where he was shown as sitting in the front row, he expected to be in the front row, I believe.

Unlike the lady referred to by the OP, he did seem to be genuinely confused, although an apology for disturbing us and accusing us of sitting in his seat would have been nice.