I have no problem with the girls looking to steal signs as long as it doesn't absorb them. Last year at 18U, my 3rd baseman was great at learning the batting signs. I would move her up thinking that they were going to bunt and she would shake me off and call out a code to the defense.
I was amazed at her and with all that-she was one of the most softball knowledgable girls on the field. Not just a great player, but had the mentality of knowing what her entire defense should be doing based on what the third base coach called and the pitch selection call.
I am totally fine with the girls picking up (sorry I don't like to use the word stealing when talking about players) signs, but not adults. My DD went through that and she got frusterated at the yelling out a pitch as it would distract her and mostly they were wrong anyways. Typically the parents have no idea and it just upsets the players on both teams and makes the parents look stupid which makes the organization/high school look stupid.
Any batter can look at a pitcher and slightly figure out the pitch location and somewhat of the pitch selection (it coached properly). I teach my girls to focus on the hip, power line, and actual hand on the ball. This helps them to keep their eyes on the ball even more closely to see it coming in. While all pitchers are different, not a lot of them change things up during the second time through the order. In the dug out, my girls are taught to watch the pitch selections, body placement, and hip movements. This makes them more confident while batting. JMHO.