Why does my Girlfriend gets mad when I win an argument that she started?

Even when everything's fine, she tries finds the smallest irrelevant things to start an argument about. I end up winning these arguments most of the time then she gets angry than later apologises.
I've noticed that many times she only starts these arguments not to discuss something but for the sole purpose of winning which she usually fail at. O_o
She's not the only girl I met that's like that, few girls i dated before are like this they also get angry when I win.
They start it for no reason, I win they get angry then sometime they apologise, its always like that.