Please do not let your own misgivings about "I'm just jealous of their time together" blind you to the very real situation where he is pouring all HIS ambitions for sports into her. He is undermining her academics with his comments and he is teaching her that academics is solely in the service of being able to play ball. When he tells her about the minimum GPA to stay on the team, and talks about college softball scholarships but never about academics or majors, he is teaching her that softball comes before her education and that all that junk that goes on in class is just stuff to wade through while her real focus and goal is her sport.
She is not well-rounded, mom, and you know it. Don't let your own fear -- fear that you're only motivated by jealousy -- keep you from helping her. You are absolutely seeing the big picture here and your husband does not. This is also damaging your marriage in a very real way -- your husband and daughter have formed a relationship that does not admit you into it at all, and while it's fine for one parent to be close to a child, the parent should be adult enough to see when the other parent is being excluded to the point that you are.
I second the idea below of you and your husband seeing a counselor, perhaps starting with the two of you talking together with the school counselor who handles academics at her high school. Frankly I might even talk to that counselor privately and alone, in confidence, and express the serious concern that the girl's education is being undermined by the intense sports focus. Then have your husband come in, if you trust the counselor not to break confidentiality and say that you were in earlier to talk. (I don't normally want to say, go behind his back, but in this case you may need to prime things a bit.)
If this doesn't work, your husband needs to hear from someone who is not you. Does he have a male colleague or friend who is a good enough friend of yours that you can get that person to intervene? Because, I hate to say it -- your husband isn't going to listen to you because you aren't part of the softball inner circle. He isn't respecting you as his wife or as a mother.
If the school counselor and an approach by a friend fail -- time for marriage counseling because the larger issue here is that he's self-centered to the point he isn't being an adult parent; he's being an ambitious coach, and another issue is his lack of boundaries (he's overinvolved in her sports life) and his lack of respect for you. Plus, you may have issues you want to discuss about why you've let him do this for so long, and how you can get your child back into a balanced relationship among three of you, not just a relationship with dad and a softball.
If your child gets injured and can't play any more; or loses a scholarship due to injury and has no prospect of college ball; or something happens that she loses interest -- what will he do then? Will he basically dump her as his buddy, or pester her to play injured, or rail that she gave up? Does he know her beyond knowing her as a softball player? I would ask him about these things.
Does he know that she says "I still want a life"? When she says that do you let it slide past or do you halt, look her in the face, stop everything and say, "OK, I'm glad to hear what you want. What else do you want to be trying?" Give her the shock of hearing you ask her that directly and if she stutters, uh, I don't know, I just know softball - have some ideas ready. Will she be strong enough to flout Dad if he says no, you can't do anything else? Will you?