The summary of her dissertation is really interesting, thanks for sharing! But I think OP's point was "countries who trade with each other are less likely to go to war", not "countries who trade with each other never go to war". And I think OP is right.

"So war does not necessarily stop trade. And thus trade is no prophylactic to war." Seatbelts do not stop people dying in car accidents. But seatbelts do reduce the chances of dying in a car accident. I know I'm being pedantic, but it doesn't have to be all-or-nothing. Even a prophylactic that works 1% of the time is better than nothing.