Some things to consider regarding a peel drop:  
The more you can throw downhill, the easier it is to get it to drop.  Give me a mound!

The taller you are, the easier it is to throw because you are higher up.

The bigger hands you have the easier it is to throw (done properly = more revolutions)

The closer you are to the batter, the more you throw downhill, so the more the batter moves up in the box the more you are throwing downhill IF you adjust and you pitch to the batter.

The strike zone is where the batter is-----the batter takes the strike zone with them wherever they stand.

The onus is on the catcher because a properly thrown peel drop will be in the dirt more often if the batter moves up in the box and the pitcher adjusts accordingly but the catcher does not.  The catcher must move up and she then helps herself and the pitcher.  She should do this automatically.  The pitcher cannot throw to the plate; she must throw to the batter.  A batter standing in the front of the box may require more concentration and brain power but does not negate the drop, the peel drop that is.  To me it was like playing the piano.  You see and read and react accordingly. 

 A flip drop (roll drop) is more difficult to adjust to a batter being up front in the box.  This pitch is slower and also depends on some movement away from the batter to be effective (about the width of two balls for girls is good -- down and out).  Because the pitcher cannot snap up on this pitch with her hand hinging over the power line at release and needs to carry her hand over the top and in front of her, it is not likely she can adjust to the batter setting up in front of the box very easily as she is not throwing "down" as easily as the peel.  

I would only throw a roll drop when I wanted to throw a high drop (its off speed, different looking, and I am bored).  I could throw a high drop with the roll because you don’t have to throw down as much as you do with the peel.  I think the strength advantage a man has in his forearms affords this better and few girls are able to do this well.  I had a teammate that threw a high drop this way and when he was able to lower his rise ball he would have a great day as there was little to no differential height between the rise and the drop so the ball was closer to the batter before he could detect vertical direction, and few could.  

 The roll drop is over emphasized in girls’ softball.  Much better is to throw a "screwball" out of a peel drop style of release.  BUT, any pitcher who has to depend on the horizontal movement of balls curving and screwing is limited and will only go so far.  They will have a day sometimes, especial in the 13-14 year old range where batters haven’t seen it much, but later, the good hitters eat them up.  This is why I teach my students the peel.  I sit on a bucket right beside them and work on release, sometimes holding onto their hand and working it for them until they get it.  If you could look at the release of a peel in slow motion, the back of the hand should be above the ball just before release and the thumb under the ball directly under the first two fingers.  What is great about this is that this is the same set of mechanics that also generates more SPEED.  It’s the same principle as swinging a bat and your wrist is the bat propelling the ball.  

How a roll drop ever became a DROP and a peel a fastball (IF thrown correctly), I will never know.  Frankly, I think there are some marginal instructers who did not play the game who have made a buck selling what they didn’t know and it stuck and it hurts the game and is unhealthy for the girls.

When a batter stood up in the box on me, he just told me he has trouble hitting my drop.  He is going to get one for sure, likely three.  He also gave something up because he is more susceptible to bite on rise and change-ups by standing in front of the plate as compared to the back.  He is enabling my good time and making me decide which is more fun to get him out on.  I don’t know of any of the Men’s’ major level pitchers that I played with/against that were national tournament caliber that would not tell you that peel drop, change-up rise were their 3 best pitches and if you want to stand in front of the box please be my guest.

 Doug  Plank