I don't see the connection with the Montreal screwjob myself they seem like two completely different things. I would say its iconic because it was one of the first big blows landed in the Monday Night Wars, it may seem petty now, but at the time it was exciting.
To me she mattered as she opened a lot of doors for females in wrestling both as personailties and as wrestlers. She was a key part of the Dangerous Allience and was the first major woman to be pushed post 80s in WWF. And by the way I always found her hotter than Missy!
It led to the MSJ because after what she did to the Women's Title, Vince didn't want to take the risk that Bret would do it too with the Heavyweight Title. Bret could have had his storybook farewell if not for her unprofessionalism.