She has the yips. Try this: Go to a field and throw about a dozen balls all over the area she would normally field . You go to first base, she is at the pitcher's plate, and when you say go she runs up, picks up a ball and throws it to first as quickly as she can without thinking. Then she goes back and does it again and again. The speed is the key. Repeat as needed until she gets comfortable with it.
My younger daughter had that same issue for a while. This is what we did and it cured her pretty quickly.
My younger daughter had that same issue for a while. This is what we did and it cured her pretty quickly.