Try a game that I've used.
Using tennis balls (a bucket of 24) and a tennis racquet, pitch to her. (later on have her BFF or another player pitch) in gym or out on a field or a back yard (but outside is better) and just have her whale away. Hitting the ball as hard as she can as far as she can where ever the ball is pitched. Have her use two hands and swing the racquet like a bat. Hit all the balls and then pick them up and then do it again....
This is the hard part...... do not any under conditions criticize her or help her swing mechanics in anyway. Praise all the hard hit balls and all the swings, every time she takes a cut find something nice to say about the results, tease her a little or do a play by play.
My guess is that your dd is a perfectionist, is carrying a 4.0 and has her college all picked out. She doesn't do something unless she can do it perfectly. Stop the hitting lessons and the criticism and concentrate on just having fun with her. She has to learn to pull the trigger, but she is worried that she isn't going to do it right and is paralyzed. It is all mental. She just needs to break through this wall. A lot of fun swings with great success should do the trick.
Come on dad smile, have a little fun, she is only 8.