Unless someone points me to a violation, I have no problem with what players do to warm up (or being outside of the dugout) UNLESS or UNTIL</b> it affects the game.

In the case you mentioned, for instance, if the player taking her warm up swings delays the game, I might apply the proper remedy.

(edited to add)

Another issue that sometimes comes up (more often with the next team scheduled warming up) is the problem of loose balls comming on the field. In that case, f the problem repeats itself, I ask them to move or stop.

Also, if safety is an issue (off the field), I expect the TD to handle it.

I don't know if ASA has a stance on this, I imagine it would be up to the TD, unless as stated by others it affects the flow of the game.

I umpire mostly HS now, but will ump a couple ASA tourneys during the year, and unless someone complains I don't worry about whats happening outside the fence.

...if it is outside the confines of the field. 

There is no FED rule that requires the catcher to wear a mask outside the confines of the field.

(added: Not sure about ASA)

In FL, that also includes "warm-up" areas which to me would include areas adjacent to the field (just outside the fence. Especially if the pitcher is, well  warming up!.

That is what I have been taught in clinics and (even evealuated on). Don't know if I could show it to you in writing.

It can be my jurisdiction, but I don't pay attention to whats happening outside the fence while the game is being played.

FED 2-15

The confines of the field includes the field of play, the designated dugout/bench area, any enclosed or clearly marked area designated as a warm-up area that is adjacent to the field and within the view of the umpire(s).

Then Rule 3-6-6 says who is permitted to be outside the dugout/bench or designated warm up areas.

Catcher's are required to wear a mask when warming up the pitcher within the confines of the field and players are not allowed outside the bench or designated warm up areas unless they are the 3-6-6 exceptions.

What I have been told is players have to stay within the confines of the field during the game, with the exception already noted (bathroom, retrieve foul balls).  The confines of the field include any designated warmup area.  So basically at pregame we determine where they can be, if they are outside of there they need to get back into the confines. 

I have been told not to allow players to warm up like is described in the OP, and yes if a catcher is warming up a pitcher who is using a pitching motion she needs a cathers helmet on (not a batting helmet). 

What area do you work?