Great question. You cannot ignore stats, but you have to know your team. Chemistry is huge, leadership, communication, etc. No simple answer, really good coaches know their players and pick up on things not always measurable.
I think baseline best practices is where you start, basic softball 101 as far as setting up defense and line-ups. But first, what type players do you have? You can't play fast and use small ball with a team full of big power hitters, etc.
I would throw error stats right out the window, I hate them. If a player has "too many" it will play out and you will know, no need to hammer it or let it cloud your judgement by micro managing it. Use every error as a coachable moment to use in your next practice or during the game, but do it with tact and not to tear down your player(s). You can use really poor at bats also, like 3 bad swings and a K with players in scoring position, instead of trying to work the count to move runners. By teaching the game through moments like this, each player understands that your not attacking them, but just want them and the team to get better and every example is useful for that.
Batting avg is of course powerful, but still, does she bat .280, but have a ton of ROE, FC, low K's or solid hits that are being fielded? This is a case of a hitter hitting the ball, just stay with her and let her be a hitter. High K's are never good, that cannot be ignored and needs addressed, especially if a lot of short at bats.
The more you know your player(s) the easiest it is to adjust lineups as you go also. Communicate with them, so they understand the plan and why a change is needed. Many coaches are really not good at this.
I am a huge advocate of tons of actual games and scrimmages, some coaches are heavy into just practicing. I think both are essential, but games are where its at to determine where to play everyone to be most successful. Gives you time for some trial and error also, before big games come up. Let them play loose and fast and see where you need work and what they can do.
Just a few thoughts.
Good luck!