Are you sending it to her first for proofing, and THEN she's emailing everyone with changes? Or are you just emailing everyone without getting it proofed?
I've learned the hard way to always, always, always get anything that is about to sent out proofed ahead of time by whomever asked for it to be done. Same token, when I'm asking someone else, I ask that they shoot it over to me first.
Constant corrections (especially en masse) just looks unprofessional. It looks like no one is talking to each other, or someone is sending things out before they've been proofed (aka power struggle).
Now, sometimes agendas change, points change, and there's nothing to be done. Things change on the fly, and an update is better than none, but when it's a consistant pattern of behavior, I drop that particular vendor as quickly as possible, because it's obvious they can't get their act together.
HOWEVER, if it's MINE/ I'm lead and someone comes along changing MY work I get ticked. I did it how *I* wanted it, it's MY "thing". Someone can ask me about x, but I have the final word on x.
So to me, it would depend on whether these are things she's asking you to do and you aren't sending them to her first for final okay/verification... or you are and then she's coming along behind you making corrections after she's already stamped them (making you look bad to others)... or whether these are *yours* and she's poking her nose in messing with your stuff.