It is all about getting outs. The K is the easiest out and the very best thing for the team. Nobody has to field a grounder (one opportunity for error), make a throw (second opportunity) or catch the thrown ball (third opportunity), thus the strikeout is the easier out for the team. Next is a pop-up, then a fly ball. The ground ball is harder to convert into an out than all the others. They sometimes find holes, as well, and give no opportunity for an out.
That being said, if the pitcher cannot strike out the hitters she's facing, then the ground ball is a great strategy for her if she learns how to pitch to that type of contact. Drop-ball specialists and off-speed specialists are perfect for this and can be wildly effective with a great infield. I am reminded of the 1998 WCWS final when Amanda Scott shut out the Arizona Wildcats (who were like 51-3 at that point) and beat Nancy Evans 1-0 in the final to win that year's title. I believe Scott only had three strikeouts, and her pitch selection was something like 80% peel drops. She completely dominated the game without a bunch of strikeouts....the 'Cats knew what was coming but could only manage weak ground balls most of the time.
Rise ball specialists are sometimes better off pitching for the fly ball or pop-up if they are unable to strike out opposing pitchers.
I suppose if a girl is inclined to get ground balls based on her pitching style, then it is a good strategy for her if she cannot strike out the girls she's facing. Do what works best but never forget that the strikeout is the easiest out there is and comes with the least amount of risk.
Not sure what age group you are in, but at 14 and up a drop ball pitcher who is forcing everyone to hit a one hopper to 3rd base is having an easier time of it then one who is counting on the K. If at the end of the game the 3rd baseman is icing her arm and not the pitcher, it was an easy game.