Breathe normally, and rhythmically, if you hold your breathe it creates tension that the horse reacts to. Most speed up, some slow down it depends on the horse.
Ride very deep in your seat and cause her to collect her back legs underneath her. Works wonders with my thoroughbreds
Use lots of seat and suck her into your stomach if that makes any sense.
Same issue here I first started with walking in collective and worked my way up from there with speed and control
Hey hey, I have the same issue, recently I’ve bitted down and done Warwick Shiller’s one rein stop. YouTube him. Also check your energy. Check her food, physical health and check saddle