At the D1 level, most " verbals" seem to put you on the radar of other schools, especially if it comes during the soph or junior year.
There are certainly talks that go one between a recruit and coach, prior to her senior year, but they are always contingent on the recruit continuing to meet the standards expected by the coach. On the other side, if the coach leaves for what ever reason, all verbal "offers" are off or subject to approval from the new incoming staff.
Signing the NLI secures the athletes position at the school..
D2 and D3 are certainly different. D2, with limited scholarship dollars, tends to sign more kids in the spring, after the fall signing period. The available pool of players get bigger after the fall early signing period. D3, with zero athletic money, also completes their incoming classes in the spring.
My experience ( 11 years D3 Head Coach ) is to recruit everyone, and don't write off anyone. D3 schools typically package all students in the spring, after the parents have filed the previous years taxes, and filled out the FAFSA. Whatever merit scholarship monies awarded, based on academics, along with Pell and Stafford assistance, and other awarded monies ( community based, church, endowment, work study etc) finalize the D3 students package.
The one thing I have learned at D3, it is never over. I have lost kids to D2 and D1 schools, after they have deposited, been assigned roommates and attended orientation at my school. I have also had kids show up the first day of classes, when I was told they committed elsewhere...
Congrats on your daughters signing.