Tell her that next time she dunks to make sure she uses more wrist. You don't want to mistime it and have your finger get caught in the net.
I need to come up with a really cool story for her. Something about some big, mean, playground bully who was charging hard in the paint. She shut him down hard, and made him slink away in shame, but it cost her a finger.
When we first married in a 4 week span DW broke her nose while I was teaching her to catch a softball (oops) and then broke her hand on a basketball pass much like the OPs DD though fracture was to a bone in the hand not finger and I was not involved in that one. Her coworkers wanted to know if I was beating her and if she needed to go to a shelter. That was a bit awkward but she got a good laugh out of so it was OK.
She could say her finger got stuck between the rim and the ball when she was rejecting a dunk attempt.