In addition to reaching out to D3 coaches with an introductory email, I suggest filling out the recruiting form on their websites. At the very least, that will get your daughter on the mailing list for upcoming camps, etc.
The amount of influence that a D3 coach has on the admissions process, as has been mentioned already, will very much vary from school to school. Additionally, it could be dangerous to assume that you can just show up at fall try-outs if you've not had any prior contact or recruitment from the school. At least with the schools that my daughter looked at (all D3), all said that while they theoretically allow any interested players to come out in the fall, their team is primarily set via recruiting. More than one coach has told us that she doesn't see the point of recruiting a girl only to cut her in the Fall of her freshman year. You've got to prove you belong there past that, and certainly need to earn playing time, but that is the same at any level. Of course with D3, since there is no athletic $ the coach doesn't really know which of their recruits will be there until they see who has officially enrolled.
The amount of influence that a D3 coach has on the admissions process, as has been mentioned already, will very much vary from school to school. Additionally, it could be dangerous to assume that you can just show up at fall try-outs if you've not had any prior contact or recruitment from the school. At least with the schools that my daughter looked at (all D3), all said that while they theoretically allow any interested players to come out in the fall, their team is primarily set via recruiting. More than one coach has told us that she doesn't see the point of recruiting a girl only to cut her in the Fall of her freshman year. You've got to prove you belong there past that, and certainly need to earn playing time, but that is the same at any level. Of course with D3, since there is no athletic $ the coach doesn't really know which of their recruits will be there until they see who has officially enrolled.