"It is your fault"

Just the flavour of returning to Italy. I went to the post office to do a mailing, but I arrived a bit late and the queue was too long: since I had to catch a train I gave up and postponed to the next day.
At dinner I complained with my sister about the slow-moving queue at the post office, so she asked me at what time I had arrived and at what time my train was scheduled to leave and then she sentenced "it is your fault". To which I was a bit unaccustomed after spending a few years in NY.