One true requirement is Academic so focus on the grades and be sure to check out the NCAA Clearing House. The term that is used is "STUDENT athlete" so you have to qualify first as a student, before you can be an athlete.
Another thing close to a "true requirement" is attitude. Travel ball coaches will put up with bad attitudes in order to win, college coaches have their schools reputation on the line and every single college coach I've talked to or heard from wants girls that can control the 6" between their ears at all times. That means no throwning tantrums if umpire makes bad call, you make an error etc. They want positivity.
There are some teams who's coaches seem to have "prototypes" that they feel are the right "build" for college ball and every girl looks like the others. But vast majority of teams are looking for girls that can play the game and help their team win. At a D1 college tournament this year I saw one school that I thought was a 14U team just coming there to watch because they were so small compared to some players on other schools. There are certainly some very big, very strong girls playing D1 ball, but overall college teams look just like most other teams. An old analogy that really fits is "It's not the size of the dog in the fight, it's the size of the fight in the dog." There is no prototypical shape when it comes to a heart for the game and a desire to do anything to win.