dam3391: As much as I loved eggshell's answer, I think yours is a bit more sound. Remember when you were a kid and somebody started repeating everything you said? Made you mad, didn't it?
If you listen to birds, not just turkeys, exact repetition seems to be the thing that triggers an aggressive response. My guess is that it comes from deep down in the brain. If you hear back exactly what you're sending out, it makes you mad. I can be sitting out back in the morning, sipping my coffee and see this played out. Little bird comes and lights down on a branch and chirps. Some distance off, some other bird calls back. The two get into a calling match and before you know it, the two are scrapping and pecking at each other and finally one of them has to fly off.
The key to making it aggressive, if turkeys are like other birds, is to come back right away-- even walk on the other hen's calls, and give her exactly what she's laying on you. If there is a delay in honoring the hen's call, what you're saying is that you understand the hen's out there and that you're giving her a pass to walk on through as long as she keeps her distance. With no delay in the response, you're telling her you are willing to fight.
Now, this may or may not be a good idea. What I mean to say is that if you call that other hen out and she's not in the mood to fight, she may make a wide arc around you or even turn around and go the other way. She's sizing you up on your disposition, and capabilities. She's also got to figure in her own capability. All this she's trying to cypher out of your call.
We used to have a bunch on here that used to make fun of folks that talked about "henned-up " turkeys. It's for real. There really is a phenomenon like that. And busting through this problem can be insurmountable given the turkey hunter's ability to dissect the problem and make the right call to respond.
I offer another way; I'm not all that good a caller. I admit that I've gotten into this and said something to the hen and 40 yards off, she's turned around and gone off in another way, leaving the gobbler 60 yards back in the woods never coming close. In fact just about every time I try and pull one of these fancy tricks, I end up getting a lesson in the folly of pride.
What I like to do is offer up the disappearing hen trick. First, I show that I'm ignoring the other hens. I make calls that show I can't hear the other hen. This is easier than trying to match her. In essence, I'm transmitting a scenario where there is no communication going on. I don't mean saying "I don't hear you!"-- like a taunt. I mean calling like you just don't hear the other hen. Then, I start feeding a little. Clucks, purrs, and scratching. If I have somebody along, I have them cluck and scratch too. We're just a couple of little hens, out enjoying our morning meal. The opposing hen will then have to call to tell us she's coming, and warn us of her approach. We continue feeding like we don't hear her. She comes closer. We shut up. "Poof!" We're gone. Did we run off? Were we scared off? Did we just go behind a fold in the land where she doesn't hear us? Silence.
The hen comes though, looking for us. The gobbler comes trailing behind. a few minutes later.. . Boom!
At least that's the theory. It works once in a while. I called one in for SuperCore last season that way. The point is that this method might be better way to go if you're just a beginner and can't do all the fancy calling.