I have always encouraged my DD to field everything she can with reasonable effort. I don't want her diving for balls, but I want her to be aggressive.
This is where we're at, although my knucklehead will still dive for balls! We just finished up Fall ball this past weekend and ironically enough us 3 coaches were just talking about this very subject! All 3 of our pitchers also play MI, one plays 2B and the other two play SS, all 3 have excellent gloves! Makes a huge difference, not only from just flashing a little leather but making smart decisions with NO hesitation!
My DD plays HS for a small Christian school, last year we beat a much better team than us to get into State. Their pitcher was a D1 commit and was handling us pretty well, one of our left handed lightening bolts bunted a ball straight back to her and the pitcher threw the ball 10 feet over the 1B's head, then it happened again! Us coaches all at the same time said, "this girl can't throw overhand!" We started hitting and bunting everything back to her, she made either 4 or 5 throwing errors that game and we beat this team. It was sad and I felt so bad for this girl cause she's a great pitcher!
A pitcher fielding a ball or knowing which balls to leave alone for her fielders is just one aspect, I see more pitchers get into to trouble by making this one fundamental (or lack of) mistake, not stepping towards their target when making a throw!! Every time my DD fields a ball in the circle, I quietly in my mind say to myself.......step!