This move 5.c3 looks coached/prepared, else it was accidental, but I have never seen this system before. It’s actually not a terrible move, may be okay, but I have an antidote for it now, but it’s quite elaborate I must say.
In the game, I decided not to take any risks, perhaps because she threw me off guard so early, and I am playing with the Black pieces anyway. As Black, the game has to be _your_ work of art, not White’s, so it would be time-consuming to want to play it best OTB, although I still should have. Their coach reads my blog from time to time, so I can’t give too much away here.