All horses will get hyper in a new place, you have to train them not to be, they don't learn that on there own. If you need a chain to control her then she needs a lot more ground work. Just keep in mind that it is called a "stud" chain.
I don't think (know) you don't need it, if your filly gets hyper then just fix it a chain is not the fix, you don't want to have to use it every time you bring your harse somewhere. I don't even have a chain I don't like them, I have used them and hate them they are way harsh, a rope halter will work better when tied right. A rope halter also goes across there pole.
I agree with Flying B. You never absolutely need a chain, not even with stallions. Its true that a chain can be used responsibly, but by no means is it necessary if a person takes the time to ensure that the horse is respectful and trained on the ground to begin with. It doesn't matter how hyper the horse is. Take it in an enclosed area and work it on the ground. Teach it manners and train it to respect you. All it takes is effort on your part. If the horse trusts and respects you and you've spent sufficient time correctly working with it, then you will have control of the horse.
I think that maybe you need to work on your own confidence more. I'm sure you're very capable of working with your young horses so that you won't need a chain. I'm sure you also use them responsibly, but the fact that you think you NEED them points at your fear of being out of control. Believe in yourself! Plus, if you lost your temper or got frightened and started jerking, its easy to upset the horse and deliver unecessarily harsh punishment. You may very well do it without intending, and the horse can quickly get head shy, or become unruly and dangerous because its upset with being unfairly handled. I think you are more likely to end up with an "out of control" horse by relying on chains and not ensuring that you can control your horse with the least force/contraptions possible, which I believe is the true mark of skill, harmony, respect and control in a relationship with your horse. Have faith in your abilities. I'm fully willing to believe you have what it takes if you just give it a try.
We tried using a chain on my old mare Mattie when she was young and unruly. I had very poor results. The only thing it did was make her angry and headshy. It is true that you ask a mare, so trying to force her with a chain wouldn't do any good.
I'm not going to jerk her around. I'm not saying she's out of control, I'm just saying The chain is "there" You do NOT "use" a chain it's just there so when the horse gets ahead of you it's puts some pressure. Problem that come with the chain are becuase people put the pressure.
If your horse is passing you the chain will not fix it, just use a rope halter and when she goes ahead of you back her up that will fix it. Trust me when I say you don't need a chain, I have had the wildest horses on a rope halter. I have had 3 and 4 year olds that have never been handled but to give it's shots and at new farms. You just have to know how to fix it. If you horse is dead to a snaffle do you go to a curb? I hope not because then it will just become dead to that and then port and then what? If you go to the harshest right away then you have nothing else to go to.
I think you are the one that needs a little training.
Yeah you don't need one on young horses, I think it is an easy way out for the owner. Its easier to just slap on a stud chain, and not take the extra time and effort it takes to gain respect.
When I bought my stud colt, the first thing I did was take the stud chain off. He reared and tried to run over me but w/ a little clinton anderson lunging for respect level 1 and 2 he was perfect.
Like I said sure you can use one, but you are being lazy, and like most quick fixes you have reprocusions in the end. Like a head shy horse, brusies nice, and some times irreseravble damage done to the senistive cartalidge in the nose.