Hi Markie. Welcome to the Uni. Sounds as though your filly is progressing well - but still very much a baby. When Monty starts a youngster, once he's established that the saddle is ok & the rider is ok ( over 3 - 5 days ) he moves outside the roundpen but brings into play an experienced horse for the youngster to follow & copy. Your filly is motivated to return to her herd & if you don't have an experienced horse & cooperative rider to help you at this point, I suggest you use the fillys enthusiasm rather than trying to fight her. Trotting towards horses is teaching her that free movement is not only possible with a rider but rewarding. Controlling your breathing will help her slow down as will the realisation that having a rider doesn't mean she isn't necessarily required to ' deal with the whole world ' all on her own. I understand your concern that she is taking control but you & she will both gain more if you ' harness the positives ' from this situation & instead of fighting her, actively use the herd by riding quietly along the fence next to them. You can ' ween her off this habit ' by giving her a schoolmaster to follow & imitate next year when she's older, stronger & more ready to deal with work. Cheers, Jo.

Hello Markie; From your description of what you are experiencing with your young horse, I would say that your horse is responding more to the draw that she feels from the other horses than she is to your request [cue] of slowing her down without rein contact.
Question that I would ask:  How young is young?  How old is she? How much time has she had in learning to be ridden?  What, in your opinion, is the disconnect from the ground work to being on her back as far as the whoa or slow-down request is concerned?
When we train our young horses, we all have ideas of where and how we would like them to respond to our requests when we ultimately are controlling them from their back.  This is where things can be frustrating with horses.  Two things that Jo has mention really could help turn this problem in a different direction.  #1 A school master horse to ride with.  This second horse would create a DRAW with her energy and responses to being ridden under the control of a rider.  #2 The second horse will help bring down the adrenalin level by relaxing the younger horse in your riding relationship.
  It is VERY IMPORTANT that our horse learn in a relaxed manner.  WHY?  -because they love to please-which means to do what they have been asked to do   ..We as trainers MUST put whatever time it takes to make sure that we communicate exactly what and how we want the horse to react.  There are progressive  steps that must happen for you to help the horse understand what you are shooting for.  In your case, for her to slow down as your movement quiets in the saddle.  This can take some time, so tip the playing field in your favor by getting your horse to look for answers. The first thing that I might suggest would be to ride your horse away from the other horses a few strides, then ask for a whoa.  When she gives that action to you, ask her to back up a few steps, then walk ahead a few steps and whoa again with an immediate back up request .  Take two steps back, then ahead 6 strides, slow down with your seat with REIN PRESSURE, but not to a complete stop; ride forward and then turn back toward the other horses and allow her to go up to the fence and stop as you slide back in the saddle.  this time with  NO REIN PRESSURE .  If she completes your request, then PAUSE AND PRAISE, and congratulate yourself.  With the exercise, you are using your horse`s seeking mechanism  [DRAW FROM THE OTHER HORSES]  to help her understand what a riding relationship is all about.  When done correctly, everyone wins. Do this many times for days   With this in mind, after asking your horse to slow or stop in the same place each time, create another draw for her as you ask her to ride on from the place where you have continually stopped on all of the other attempts.  Now you have ridden by a THAT place where your horse has anticipated a slow down or a stop and as a consequence put her on high alert for your request to slow or to stop.  Because of this change, you are now in her MIND and she will anticipate your next request as a LEADER.  This is a beautiful moment for both horse and rider.  It`s called HOOKING ON; only in the saddle.
I hope this will help
Bud 

Thank you for all of the input. She is just about to turn three. I started her under saddle in the summer. She does well stopping completely. It’s more when I ask her to walk on she trots instead. And when I shift in the saddle she ignores it thinking we will be going back to the other herd members. I should add I ride inside the paddock with the other horses. I haven’t taken her outside yet as I wanted her to be Well schooled on the reins and cues. Also I have no older horse to ride her alongside and no other riders. So that is difficult. I also have to arena or separate paddock. Thanks again.