It's probably a combo of what she said and an awful lot of the white noise in general about c-sections that is causing what is upsetting you.
Love you gave birth, no you might not be able to help her much with what to expect with a vaginal birth, but if she wants to consider that birth plans can go awry, you could yet prove invaluable as far as "what to expect if you end up with a C" goes.
Mind you, I'm not sure what good other women's expereince do really.
Unless they were all LYING THROUGH THEIR TEETH to me before I went inot labour.
"You'll be fine" my left bum cheek.
Unless feeling like you are being painfully squeezed to death by a boa constrictor is somebody's definition of fine ?
I wound up with a C (thank god, cos my plan B was dragging myself to a window and throwing myself out to make.it.stop) and remain truely grateful.
Maybe cut her some slack due to late pregnancy grumpyness and fear of the unknown rather than it being a sign she is dissing the way you gave birth.
I have a slight suspition I was not diplomacy itself in those last few months. (photos of me looking like an enraged hot air ballon and all the people around me keeping a safe distance offer a clue)
Perhaps when she talks she is looking to offload rather than get advice ? In which case maybe just somebody to listen and comiserate is what she needs ?