Tyto, my kid thought the competition was hilarious and fun, but then we’re from a state where sports rivalries are taken very seriously. He went to a hockey game one year that was scary in its intensity, but I think that was more the alcohol than the rivalry.
I wish that I could find the post I wrote in March 2014 (I think) after the car accident that killed three Carleton ultimate players. It was a bit of a love letter to St. Olaf. As you might know, Carleton has a tradition called Friday flowers, where you can put fresh flowers in the mailbox of a friend or teacher or child (you can arrange it long distance). The next Friday after the accident (it happened on a Friday evening on the way to the airport as various teams were headed to tournaments), St. Olaf arranged for every person on the Carleton campus to receive a flower. It was such a heartfelt, lovely gesture. As an ultimate mom whose ds already had made it to the airport that fateful night, I’ll never forget it. I’m tearing up now as I write this. St. Olaf always will hold a special place in my heart.
Unfortunately, a few months later Carleton had the opportunity to return the favor.
http://www.today.com/news/carleton-college-fills-rival-st-olafs-mailboxes-flowers-1D80225186
Maybe because I follow all the ultimate teams, I see the love between those in that community all the time. The Carleton DIII women’s team played St. Olaf’s in Georgia last weekend. After Carleton won, here’s what the Oles tweeted: “9-15 but really Nofo love-Nofo love (but the 
kind of love not the tennis kind of love) gg @eclipsethedisc #cowscollegescontentment” So, for some, it’s a lovefest of a rivalry.
I’ve found most of the kidding good-natured, not truly vitriolic, but as we say on cc YMMV. Good luck with your dd’s decision. Let us know whether she picks either Nofo school!