Arguments for Christmas?

Is there something tradicional that Christmas season is always the a time for arguments? So I have been paying my wife's nephew to drive my truck to our new house with materials. One day I asked him to do a run and he said sure but could he use the internet to fill out a college application form. Yeah sure. So he spends two hours deciding what to put on eight lines and when he finished it was too late for him to make the materials run. Ok fine. I didn't make a peep. So yesterday, a few weeks later I ask for another materials run and he says (on the phone) can I use the internet for something quick? I say yeah ok but I'm raising my eyebrows . My wife is watching. Later she is furious. According to her I have shown myself to be a selfish bastard with members of her family since I didn't "want" her nephew to use my computer, ( does anyone remember I said yeah sure to him on the phone?) We are now in a tit-for-tat. She left mid-morning for the whole day to hang presumably with her family arriving home at seven pm. I guess she sure showed me...?